Prophex,
For a good primer on electrics, go to www.utahflyers.org look up Darrens blog, will help get you started on the right foot.
Esc 10, 25, 35 is amount of amps it can handle continuously. What Matt was getting at was pack will determine how many amps your motor can pull safely. Hey, Ive been there, switched to elecs little over a year ago. I know where you're coming from. Get the recommended set up.
Then look at a calc program like Motocalc, 30 day free trial, www.motocalc.com
You can build your planes specs on it, then play around with different motors,props, packs, esc's

Try to think elec in gas terms. The battery is the fuel tank, the motor is the engine, the esc is your throttle servo. Big engine/ motor means high fuel/battery drawl, etc. Might make the switch a little easier.