hey i dont really know crap about systems and i want to learn a little b4 i spend to much money or get ripped off

this guy wants to put 4 10's and a 4ch amp in my truck and he said that the amp would put out 100 watts to each speaker, im not sure if thats very good for how much im going to be paying him. if anyone can help me by saying how many watts each speaker should get and what a 4 channel amp is next to a regular amp id appreciate it, thanks