We bought our Class C (new) in January - and our dealer gave us until May, to find things we felt needed fixing and bring it back for warranty work. Granted, this is Michigan and a lot of folks don't think about camping until May...
While I understand what your dealer is saying, and they sure don't want to tie up a service bay any longer than possible - I'd either get them to show how everything works - or.... give you more time to find out if there's problems??
We bought our (10-yr old) 5er after it had been winterized - and then got clobbered with relentless snow. Now we get to *hope* that the plumbing works.......