Probably over-kill on info, and I'm sure it's all confusing right now, Nathan&kelly, but I would say (among other things) the fact you have crappie at 8-10" indicates to me you would want to get some relative weights of every size bass you catch before you start removing what might be keeping your crappie in check.
4+ acres can be a very complex ecosystem, it'll take some time to figure out what you have. Keeping/starting good record keeping to analyze later is a good first step at starting a game plan for proper management.
I would also add as other have, save your money on the FHM.
