If you do your research and start off w/ a pretty good condition car, then mod it in the correct manner, you should have little to worry about.
As far as FD's go this usually means 10k plus. (minimum)

Or you could go the fun route and try to find the cheapest, blown-engine FD you can, which would leave a lot more money to build the motor the way you want it from jump street. It really depends on how much cash you got and what you want out of the car.

Although, for what you'd spend to get an FD in perfect running order (either paying for a good car, or building up a not so good one) you could have a kick ass FC.... But to answer your other Q's:

The after market support for the FD is great. There's more stuff than there is for the FC (from major brands) but it's usually a little more expensive too.

OEM is OEM, no dealer is cheap. I've never had a problem getting a part from the dealer (so availability isn't a big issue)

Stock FD motors go for about 90-100k usually a lil less. IMO due largely to the stock cooling system. (T2 FC's go for about 100-150k).

They're at least as reliable as a DSM lol. Seriously its all about preventative maintainance. Stay on top of your oil changes, coolant flushes, and such and you'll be good. Upgrade the cooling system!

Can't speak on the FD, but I get around 18/25 in the FC. I'd imagine its somewhere in that neighborhood

If you've got FD money, then you can run to the tuner shops I suppose. Mazport does good work, but it'll cost you good money too.

How a rotary works: Howstuffworks "How Rotary Engines Work"

Rebuilds are not done every 60,000 mies unless....
A) The car is owned by an idiot that neglects maintainance
B) It is a street/ race car

I'd give it an 9.0/10 due mainly to the sub par cooling system, cheap plastic interior pieces