Mid-time valve work on those big turbocharged Lycs is normal.
Couple of recent ADs that have the potential to be expensive:
https://rgl.faa.gov/Regulatory_and_...2906b48286258178006891ae/$FILE/2017-16-11.pdf
https://rgl.faa.gov/Regulatory_and_...08d310108625813e0048586e/$FILE/2017-11-10.pdf
I replaced part of the exhaust system as per that second AD. It wasn't cheap. $7K or so Canadian, which would be over $5K US. Make sure that this system has been inspected closely and that the Lycoming SB has been followed to the letter. Exhaust systems are not something to casually dismiss and you don't want to be the one stuck with fixing it.
https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=48513
The G1000 should have the SVT already in it. There's a really fat fee for the card to unlock it.
The KAP140 runs off a turn coordinator hidden behind the panel, alongside the other standby instruments. One more mechanical instrument to take care of. I wish I knew why they didn't just mount it in a hole so it could be used as a standby. It's there anyway. Maybe it was an electric TC; I don't remember now. No good as a standby if it was.
The G1000 uses a sealed lead-acid battery, located behind the PFD, and it needs an annual capacity test. If it fails, the new one isn't cheap. Don't leave the standby battery switch off when flying, thinking you're saving it. You're not. It needs exercising. And if the power should suddenly fail, you're now waiting for the system to reboot if you left the switch off.
If it has the Amsafe shoulder harness airbag system, there are periodic replacements needed of some stuff like the sensor under the floor and the pressure cartridge under the seat, a little bomb that has something like 6000 psi in it. Disposal of the old ones can be a bit of a problem. We took ours to a quarry where they put it in the drill hole with the explosive and blew it up when blasting the rock.
These modern systems mean more maintenance. One has to consider that when buying.