That is a pretty aggressive first project. To read 4 channels real time each at 50 hertz, you will need to use interrupts. Darrel Taylor's interrupts http://darreltaylor.com/DT_INTS-14/intro2.html are the easiest to use, but there is still some complications to use it to read the pulses. I have an example running on a 12f683 reading 5 channels, so it is definately doable on a 16f884. It uses the CCP1 pin, but it uses assembly for the interrupt routines.

http://www.picbasic.co.uk/forum/showthread.php?t=12657