LOL I am new to all this as well. We came from a TT to a C. There is certainly more maintenance with a C but no more than the truck that tows your TT.
As far as reliability of the house part it will be the same as your TT which is to say probably not very good! LOL! The Ford chassis will be about the same as any other Ford which is average to above average. My hope is the E450 will be above average reliability. The design hasn't changed much over the years. Ford has had plenty of time to get it right. I mean the front I-beam suspension has been around since before I was born!