What follows is a combination of my experience and having combed every resource on the web quite recently, since I was also looking to get GBRs after having minimal success with them in the past.
If I was starting from scratch, as you appear to be, I'd go the following route:
First, establish your tank. 29g is fine. Lots of plants, stones, driftwood. Excellent filtration, but not too much flow. You really want a mature, stable tank, with excellent water quality for these guys. They like it toasty, 80deg+, with 82-84 optimum. This will impact your choices for stocking, since not all fish/plants/inverts will be comfortable at these temps.
Next, I'd get six young fish from a reputable source, preferably a local breeder. Let them pair up on their own. You'll probably find, depending on your 'scape and your fish, that most likely one pair, or possibly two, are all that you'll want in this tank. Re-home the outcasts as necessary.
At that point, you can decide what else you want to try with them. As cichlids go, they're very peaceful, except when protecting a spawn. Even then, they're not exactly terrors - they'll just chase everyone else away from their nesting area. The main consideration is that their tankmates should also be very peaceful, what's sometimes called "dither fish". Basically, non-territorial fish that aren't hyperactive, or significantly larger than your rams.
Mine are in a 26g bowfront that's been running continuously (with the occasional re-'scape) for five years. Current tankmates include harlequin rasboras, cherry barbs, otos, and dwarf platies. (Not my dream combination, but the tank is in my little girl's room, and she and my wife have a rule about "they're our fish, this is their home", so they're holdovers from previous themes. I'd go back to just rams, cardinals, and otos given the option.) I keep the tank at 80-81deg to accommodate everybody as well as possible, while making sure that the rams are comfortable. I was fortunate and was able to pick an obviously mated pair out of my local LFS's stock - they actually spawned within 48 hours of being in my tank.
All that said, I suggest you do your research here and elsewhere. I've tried to summarize mine, but you you may pick up on different things, and I'm sure I've left plenty out.