Just making sure about something because a bunch of beginners seem to think like this:
You aren't trying to amplify the 5V signal from your uC to drive the motor right? It seems you realize the current drive capability of the uC is not enough to drive a motor though.
It's better to think of the uC 5V signal as a switching signal (like a finger pushing a button) that tells the transistor to turn on and off a much larger current (a dam). This means that you can drive the motor at something other than 5V with a 5V uC as long as you connect a different voltage source to the source/drain or collector/emitter of the transistor. Similar to how you pushing a button with your finger can open up a dam- you aren't amplifying the force of your finger. Rather your finger is giving a signal to tell something else that is larger and more capable what to do.
With that thinking (rather than current amplifier thinking), FETs are a better choice but everyone has their preference.
That said, you need to know how much current your motor will draw. Connect it to a battery of the same voltage you plan to power it with in series with an ammeter clamp the shaft and quickly switch on and off the motor just to see what the stall current is (the max current possible). Don't leave it on for too long or you will damage the motor.
The 5V that you speak of powering the motor with, is this voltage the same voltage coming out of the regulator that also powers the PIC? It's not a good idea to regulate the voltage to a motor especially with a linear regulator since the load is often too large for a regulator and a lot of heat is generated and it's not really needed. Just connect it straight to the battery (through the transistor C/E or S/D of course).