I have the same rifle and bought mine about a week ago. Here are the things i can tell you from just a week of ownership.

The bolt release is in fact on the trigger guard. As for extended mags theres two ive seen that will work dark eagle custom and cdi. The first one uses stock magazines modified to allow 6 more rounds and the cdi uses ai mags if i remember. As for stocks ive seen several that work but only one or two are complete drop ins and the rest seem to require inletting mods to work.

As for the 700 i too was about to pull the trigger on one but fortunately for me the deal fell through on that one and i ended up with a whole better rifle. Heres what ive done to mine so far.