Welcome.
Perhaps there's a shortcut - buy another XC70 that has all the stuff you want!
:)
I would also think about another mechanic - as you mentioned:
The tranny fluid got changed a few months ago, and according to the receipt the "oil, gasket and filter" got changed as well.
1) would be interesting if they used the right trans fluid and it's at the correct level
2) what's the gasket and filter for?!?
3) did they reset the fluid counter (and if necessary adapt the trans)?
More info
here
With the power windows, there's a sequence to calibrate the windows to restore the auto function and ensure they don't roll back down. I would need to find that again....
Adding folding mirrors and toasty seats is nice, but requires some searching for parts. The dash GPS and phone are cool, but lacking to today's technology. Adding these extra's usually means new software to make them work on the car's CAN bus (communication network).
IMHO, the tranny is your main issue.
Ensure all the basics are right and start working up the list of more expensive items.
fluid type & level -> ensure not coolant in trans -> adaptations -> software update -> trans cooler -> valve body
If you get a good one these cars are great.
If you get a dodgy one you'll be chasing your tail and spending lots of coin.
Cheers.
