It goes pretty much literally like this:
1) You choose a rover to repair and get some preliminary analysis (it doesn't detect metals, it has troubles going, cameras are blurry etc.) Those are supposed to point you to the problematic part.
2) You play an obligatory minigame where you guide a crane to packaged rover and then transfer it to worktable. The minigame is fun exactly once, providing no challange and taking time. You can't even bang the rover into anything, because the crane automatically pulls it up.
3) You analyze the rover parts. Which could be really interesting, because who wouldn't want to wield the various oscilloscopes, voltmeters and all those other tinkery tools I can't even name. Except the analysis is performed by right clicking on a part. You click, you get 0-100% condition reading. Wow.
4) You identify the faulty part. It's usually rather clearly hinted by the preliminary analysis and at some point you can unlock the ability to see it right away, because even the authors probably noticed looking for it is rather boring.
5) You remove the faulty part. That is, you right click it which shows you where the screws are and then you right click the screws one by one so they go "bzzzzt clink" and disappear. On the bright side, unlike when I'm actually doing this at home, you can't lose them, which is pretty great. If you're unlucky, the part can't be removed before you remove another part, in that case see point 5)
6) Some parts separate into subparts. In that case you carry it to a workbench or soldering station where you repeat previous points for subparts. To add some freshness to the cycle, if you're working on soldering station, you solder instead of screwing. I wouldn't have noticed the difference, but the "bzzzzzet clink" sound is missing.
7) You go to 3D printer, choose the faulty part and print a replacement. If you're clever, you start the printer before you go screwing. If you are not, then you now have 30-120s of free time you can spend roaming your one room workshop and admiring its emptiness. Or you can play snake on one of the workbenches. Because even the devs noticed there's nothing better to do.
8) You switch to assembly mode, which means you're going to do the disassembly in reverse order. The game shows you which part you can add at any given moment, so you don't have to worry about remembering anything. Or thinking. You just right click a missing part, then screw it in and continue till the rover is reassembled.
9) You install a remote calibration tool (guess how, a hint - it involves clicking) and play another obligatory minigame. It's like the plumber game where you construct a pipe for water to flow through, except you only have two pieces, you can freely rotate them and there's no time constraint. It's so much fun you can eventually unlock an ability that allows you to skip it.
10) Hand in the rover, get resources which you need for printing bits for the next rover. I haven't found any other purpose for them and I always came out with positive balance after repairing, so rather than "I stopped paying attention to them after first cycle" I have to say I didn't start paying attention to them at all. But you can get more resources by recycling the faulty parts. Because than... you have more resources. Wow.
And that's it. Time from time you get a skill point you can use for faster screwing or cheaper printing, which would be cool if it mattered any. During two hours of gameplay (+ tutorial) I've encountered three rover types, two of which are identical (Spirit and Opportunity). They consist of many part which might be interesting if they actually differed in any way, but they don't. They are there just to be screwed on, screwed off or replaced, whether it's a CPU, wheel, solar array or metal detector.
I had a slim hope that the game might get more fun if I got to do something more complex than "replace a wheel". Be careful what you wish for, else you may end up disassembling the whole rover so you can replace the central part of its chasis and then screw everything on again. It isn't more fun. It's maddening, because 95% of what you're doing is absolutely pointless, the only reason to mess with the parts is, that they are in the way.
During the first few rounds, the notion of working on the rovers, even if it mostly means just removing and replacing parts, is oddly satisfying. Which is what made me buy the game after finishing the demo. I was hoping for more activities, more rovers, more complex actions. Sadly, it's not the case and seeing the game is leaving early access in two days, I don't expect the final version to be any different either. So unless you're fond of right clicking, I recommend avoiding this game.
EDIT: I've checked the game after release, just in case there was something groundbreaking added. Short version - no. Long version - two new rovers. A helicopter which is rather ridiculously small, ingenuity which is rather satisfying huge. So huge it comes with a brand new table (now you have to navigate the crane to the correct table, gasp!). The table has a lift and you can move the rover up or down to access parts on top or on bottom.
Resources are still useless, the workshop is still an empty room. I wanted to try and get some complex job with Ingenuity to examine it more thoroughly, but that would mean doing at least one more repair and I was in danger of dying from boredom, so... no.