Nice, I like it!
The PS2 could make a sweet car PC! Awesome to have both the media center AND game machine all-in-one. AND, being that it runs linux and has USB ports, you've got lots of other possibilities (GPS, possibly ODBII, etc).
Hell, I wouldn't be suprised if people start modding xbox and PS2 specifically for car PC applications!
As for difficulty/learning curve, if you've moderate computer skills (i.e. can find your way around a PC, such as installing Windows from scratch), I think you'll be fine with running the Sony PS2 linux distro.
Certainly let us know how it goes.