I am just getting into the hobby. I picked up two planes at a yard sale for 10 bucks. The planes are both trainers and have engines, receiver and servos already mounted. I know 10 bucks, what a great find. Ok my question is what kind of transmitter should I buy. The receivers are both 72 MHz. Should I switch them out with 2.4 receivers or leave them and buy a 72mhz transmitter. Also will the servos fit all makes of receivers. I am overwhelmed by all the technology and varieties of radios. Thanks for any input.