Its normally not a routine thing to pull the freehub apart. In general I would say if you ride a lot then once a year, and probably leave it to the pro's as yes there are lots of things in there that can pop out.
For what its worth I have never seen the inside of a freehub in the area you are talking about (springs and pawls) being rusty. Normally in that area they get gunked up and need cleaning, greasing and putting back together.
https://buckyrides.com/replacing-car...-carousel-5749
- james