[Kidkraz]

Mickmanor, I installed a cassette toilet. My first cassette failed where the water line connected to the flush ring. I currently have the Thetford C223 and also bought a spare tank for longer camping trips. I posted some pictures in my albums. The hardest was cutting into the outer wall, but even if I could go back, I wouldn't. There's several posts of folks that changed to a different version of toilet, so you have options.
On the fan, mine is the same size as what's used for the fridge, which I've always thought as a spare in a pinch. When I pulled the outdoor shower compartment, that's where that fan vents too. No the best, but it seems to have worked well.