We got a 335FS in March same year as yours. Water damaged on passenger side roof where rubber meets Filon. Previous owner was a slob and put black roofing tar on polar white fiberglass cause that makes sense. Anywho been working like a dog to get it presentable and functioning. The only common problem I've heard of so far are the delam issues but if yours is like ours it was one of the survivors. My delam issue goes back to someone's pathetic attempt to repair what originated as either water damage or an impact.
So far aside from every free minute and dollar I've done quite a bit to this beast. I was astounded at how little material makes up the nose of the camper when I disassembled and rebuilt the master room. Can't wait to get this puppy on the road all watertight and cleaned up. Never thought I'd ever get a trailer and re-frame the nose (curved) portion. It's been a fun project. Just got a replacment checkered flag CareFree awning in this week as well as a Suburban water heater. Going to a Suburban from an Atwood conversion should be relatively easy and better quality.
As far as advise if you haven't had to deal with plumbing stuff yet I recommend making your pump/strainer/filter/etc accessible as they're items that need routine visual and functional testing. Also they used a lot of 1/4" Merflex PEX for appliances so if you ever have to replace due to a leak or bad connection I have used the 3/8" SharkBite push to fit fittings. So far so good.