Receivers come with a channel sticker on them. Does this mean it has to have that channel or can they be interchangeable?

The very short answer is that receiver crystals can be changed. Transmitters cannot. I assume you are talking about 72 Mhz stuff.

there arte variables like positive shift and negaitive shift....but if you change the chrystal in the receiver to the same freq of the transmitter...it should work

What receiver is it. Some are high band and can use any crystal that is high, some are low band and can use only the low band crystal. Some can use both. Need to know what you have.