That guy does.
Have you ever built a PC, or replaced a broken screen or battery in a modern smartphone?
If so, then dig through the threads here and the googles and you should be able to find pictures of what the inside of the MD looks like as well as disassembly and reassembly instructions.
My own comfort level extends to replacing through-hole and SMD parts that aren’t too tiny. I’ve built dozens of PCs over the years as well as a moderate amount of synth repair. I would be comfortable replacing a PCB in any of my Elektrons based on the photos I’ve seen so far.
OTOH, I paid nearly $1000 to let Toyota replace the headlights on my old Corolla before a cross-country move. Could I have done it myself? Probably, but I might have ordered the wrong parts and I might have been missing a critical tool or two. I had a month to pack and prep the car, so I paid money so I could focus on ensuring that my office and synth gear was safely packed. I don’t regret the decision at all - I had a pleasant drive and car, synths and self all arrived safely at my destination.
Given that the MD has a value in the 1-3K range, USD/EUR 200 doesn’t seem like an unreasonable price to pay for a tech with experience with these devices. If the person in question isn’t familiar with modern (that is, SMD-era) gear then I would lean towards doing it myself, based on the experience listed above.
Edit: I’m pretty sure that “replacing a PCB” in an Elektron device is a fairly simple matter of removing knobs, unscrewing screws, unplugging ribbon cables, unplugging the old board, plugging the new board back in and reversing the initial steps. Should be doable with an anti-static strap, a good toolset and your smartphone’s camera. My main areas of concern would be (1) static discharge (2) fragile old ribbon cables.
TL;DR: I’d estimate 4 hours of my time for a first opening, disassembly and reassembly of a synth/groovebox. Perhaps one hour is possible if I’ve worked on that machine recently. Two hours seems like a reasonable middle of the road estimate to me.