Kind of a broad question there don. Generally, people who know what the heck they are talking about, don't claim to be an expert. Those who claim it, generally aren't.
A projector install really isn't that big a deal, but a DIY route depends on your time, your skill, and what you want the finish product to look like. Running wire, clean look, etc, can take some time. I did all of it myself, looks great, works great, have had to redo a few things, but in the end, its awesome. I use an Epson with a 100 screen....maybe 105, but can't remember. The biggest pain for me was trying to use a hdmi to cat6 converter to run the video signal. Luckily prices have come down alot for long hdmi runs so I'd say, avoid the converters like the plague. Also, keep flexibilty in mind. I choose the smaller screen, but left room to go to 120 if I wanted in both the proj throw and surround speakers. Last month, ran new usb runs for an Xbox camera on the front wall. My cabinet looks like radio shack threw up!
Also, if money was starting to be an issue, I'd spend more to get solid, basic equipment installed right over gimic feature or brand name swag put together poorly. So, if you don't trust yourself, ditch 3d, high-end audio, motorized screens, etc. Also, this is a great time of the year for last year model sales.