Once I get an ESC for my project how do I know which controller to use? Am I supposed to know the MHZ of the ESC or something?

sorry pal i have no idea what your talking about.
any 75 Mhz reciver will work with pretty much any esc.

RC_Bob,
I'm not aware of any ESC that's designed to work with only one specific 'controler'/radio system. They are generally a 'one size fit's all' sort of thingy. The 'controler'/radio system is selected by the number of control channels required by the boat, and maybe having a few 'extra' ones in case you decide to add something later that requires one. The 'other' factor is how much the radio system costs, not to mention favorite brands etc.
The general trend now is toward the newer 2.4 Ghz systems, sort of. Mainly because they offer features that the 'older' systems don't (and they're 'new'). That does NOT mean that the 'older' radios are obsolete, or junk! The biggest 'draw' of the newer radio systems, for me, is that I don't have to worry about someone else being on the same radio channel as I am, and having to change crystals/channels. The 'extra' channels are a nice option too. After that, my 'old' AM radio system does the same thing as the new one does, at half the price. (Being cheap ain't easy - LOL.) The only advice as to which radio system I would offer is to stick with a name brand. Just makes things easier to find/fix/add to/whatever. ... unless I'm selling a radio, and then that one is always the 'best' ... sort of.
- 'Doc

No ESC's do not need any MHZ. Only Radios do. For an ESC, you would need to get one suited for the type of motors your running. There are two main types of ESCs, Brushed, and Brushless. These ESC's vary in Amps. your motor will draw a ceartain amount of amps, and your esc will need to handle that much. Say you are running a 550 motor that pulls 25a. You would want at least a 30, or 40 a esc, so when you get seaweed stuck in your prop (harder load on motor) and it shoots the amps way up, you will be ok.
Dan

Lemme rephrase my question.
I'm going to get an esc. The bk marine one with a blue nem. motor.
http://www.finedesignrc.com/motorsne...eesccombos.asp
So what do I do to find the right radio? Do I get one with a receiver? Like this?
http://www.proboatmodels.com/Product...ProdID=PRB8021

buy a DX-2 or a DX-3 and be done with the radio hunt! Though i love my 2 Nomadio Reacts...

BB modss is correct.
don't skimp out on radios. Its the "life" of your boat.
anything thing that is FM. If you want cheap there are some good radios futaba puts out.

I personally run a Jr xs3 pro and love it