Is it a problem that everywhere I look for entry level stuff I see 16F84? Will it be difficult for me to switch to 16f628a later?
Not a problem. You can do more with the other chips, but that is all part of the learning curve. Basically all of the micro chips are the same.16F, 18F The same as a Chevy and a Rolls. You can drive one, you can drive the other. Might have to look around a bit for the wiper control, but still the same.

Bet I get slammed for this analogy.