EasyC and MPLAB won't co-exist at all. You have to pick one or the other.
MPLAB won't have any libraries that are particularly useful for you like the ArcadeControl() function, etc. On the plus side, there is a loop in the MPLAB code that runs every 18.5 ms. Instead of the various get and set PWM functions, you access the values directly as variables. PWM_in# are the inputs from the RC, pwm0# are the motor outs. Most things are documented in the code and FAQs at
www.vexlabs.com