Any compressor just boils down to 2 elements: an envelope follower and a gain control that reacts to the envelope follower. The trickiest part is the envelope follower. Do a search for "RMS detector" or "peak detector" and see if that brings up anything. You will, no doubt, have to get your hands dirty a little bit with code, so if you haven't familiarized yourself with that aspect of SM yet, then you might want to.
When you get around to working on the two elements, it helps to reference the service manuals of the compressor you're trying to mimic. IIRC, the LA-2A's RMS detector isn't fed by the input signal, but rather it's own compressed signal. I know there's a technical term for this type of compressor, but I can't think of it right now.
I know I haven't offered anything concrete here, but hopefully that'll get going in the right direction. I, personally, have uploaded a few envelope follower modules (I think in the reg user forum), and also a gain control module (search for "fast compression"), so those might help. Unfortunately, I'm far too busy right now to offer anything new.