Ah, another pending convert! Excellent!
These are my suggestions and opinions. Others will chime in.
Getting into PJs requires a bit of a commitment. Using one as your ONLY display requires a bigger commitment. I would guess you're not married if you are thinking about losing the TV. My wife would never go for it. When I was single my PJ was my only display for awhile, but I did not game on it (I'm a PC gamer guy). I eventually went back to a PJ/TV setup. Watched movies on the PJ, news and stuff on the TV.
You will have a lot of reading to do, but to sum things up a little:
The primary two PJ technologies used in projectors are DLP and LCD (there's LCOS too, but then you're in the $3K+ neighborhood). In general LCDs have much less lag than DLPs and are better for gaming. DLPs have a bit more "filmlike picture " to them. BUT, there are excellent PJs utilizing either technology that will do a good job. You have to read up on them and ask questions and make the best compromise for YOUR situation. For example, I have poor light control in my living room. So I bought a PJ that gives up some of the finer black level for a brighter image. You have to do due diligence with your research and pick the machine that is best for you and your budget.
Home theater/home entertainment PJs work best in a darkened room. The more lights you want on in the room, the brighter the PJ has to be (measure in Lumens). Lumens are a good indication of how bright a PJ will be, but Lumens don't tell the whole story. There's contrast ratio and other specifications that factor in.
While good 2D, 1080P projectors can be had for under $1K, the sweet spot ATM seems to be in the $1.2K-$1.5K range. That would get you a very nice 1080P, 2D projector with enough horsepower (lumens) for a bit of ambient light in the room.
AFA using it as your only display, it's really up to and your wallet. Bulbs get dimmer as they age. Typical life these days is roughly 3,000 hours of usable life (before it gets too dim and must be replaced). Sometimes bulbs fail. They are bulbs, afterall. Bulbs cost anywhere from $250 and up these days.
Assuming you don't have a dedicated room for your HT and are doing this in your living room, I would suggest a ceiling-mounted pulldown screen, right in front of your TV. Use the PJ for movies and games and the TV for your everyday watching.
Hope this helped a litle bit.