I have that same boat, PS 205. The rust on the manifolds and risers isn't a big deal. If they start to leak, you can easily change everything out for around $400. It isn't overly complicated and it is something you can do yourself.
As for the interior, the vinyl MC used in 2000 was complete garbage. I have had to replace just about every piece in my boat. Other folks I know with 2000s have had to do similar replacements.
Wow, under 500 hours. What is the asking price?