A manufactured screen will give you a professional look. However, it's really not that difficult to make your own screen and have it look good. I sprayed a screen onto my drywall, installed a flat black border around it and it did me just fine for a few years. I recently built a screen using screen material from Seymour AV. I needed the acoustical transparency and thought I would be losing picture quality. However, the picture was every bit as good and better than my painted on screen and I also had the benefit of having my speakers placed where they are supposed to be placed. It was definitely a big step up from a painted on screen. If you don't need the AT, Seymour also sells the Glacier white, which will give you a brighter image than a painted on screen. I would highly recommend this, as the price is very reasonable for a DIY option. You're paying a lot of money for the actual frame in a professional screen and really it can be done using wood and a few tools.
If you're not interested in the DIY option and you do purchase a screen, don't spend $300 for the install - that's ludicrous. Buy a case of beer and have a buddy come over and help you out.
That's a nice PJ, but if you don't need the 3D, there are a lot of less expensive options that perform just as well and have perhaps better blacks (Epson 8350 - also has lens shift, Panasonic pt ar100u, BenQ W1070 - has 3D but not better blacks).