Just had a evo 6 come in at work as a trade in and im intrested in it but sadly know nothing about them!

few questions
1) what do i look out for on them? what goes?
2) what sort of money do these go for (dont know the millage yet but its on a v plate)
3) might be letting my mint 400atwhp twin turbo supra go for it am i nuts! lol

cheers in advance