I searched around a bit but didn't find a solid answer that quite applied to my situation.
A few things, let me start from the top.
I just bought a 2002 S60 Turbo (I'm loving it so far, very smooth ride, nice car, the turbo makes it even more fun to drive)
However, I got it for fairly cheap and it has some issues (mechanically and aesthetically)
I was wondering what interior parts are interchangeable between years and models?
Primarily asking about the interior parts (seats included; mine are fairly torn up and at some point I'd like to replace them with better ones. Seat covers aren't my style, but neither is torn leather)
I was also curious about the mechanical parts. Namely the radiator, coolant tank, and all the pipes/hoses connecting them. I'm having a coolant leak somewhere, and it could be in any one of those places (it drips from about right under the tank, so I'm hoping that's it), but I'll know for sure in a few days when I get it checked out.

Thanks

EDIT: I read on the DIM repair thread that's stickied that buying a salvage one is bad. Why exactly is that so?