Usually embedded programs are written in C... though there are obviously no file functions!
(practically any chip will do to make a paintball gun)...
When I program chips I use
Microchip MPLAB available from Microchip.com (free)
I use PIC-C as a compiler (though this is not free, though you can find free ones)
I use ICProg to program the chips.
I use a home made chip flasjing device which is based on the JDM programmer. http://www.jdm.homepage.dk/newpic.htm
(thoghmine is customise o take 18 pin and 40 pin DILL packages.
and I get the chips from Microchip as well.
though you can probably find out different solutions by searching a little more.
It's very handy to have a printout of the chip manual and to actually read it!
its also handy to have a guide to C (even if you have to write it yourself) printed to refere to.