How to sanitize interior after long-term rodent intrusion?

You'll never get the stink out of the carpet. Might as well replace it... every car's carpet gets replaced eventually. It's not the type of thing that'll make the car more valuable or ever gain you any points for being "original".

Upholstery, same thing. Unless it's a pattern or a rare material that has not been replicated/reproduced.

Mice pissing in there for how long? Rare or not, I’d rip it all out. IMHO

I can’t imaging touching that stuff let alone sitting on sitting on it. Im gagging just thinking about it.
If it is as bad as you say, only metal and hard plastic can be kept. Everything else needs to go. First of all, you will never get the smell out of it, and secondly, it isn't healthy to try and save. PROTECT yourself. The guys that have already said this are right. My undergraduate degree is in Biology. Trust me when I say protect yourself. Kern Dog is wrong. It is very dangerous.