I haven't posted in a while because I have been so busy working on school and this project. However, I finally got it to work! I got a null-modem adapter from amazon.com and hooked it up to my ancient IBM laptop.
I also got the reprogrammable gameboy cartridge done. I will post the pictures and info on it soon. If you are reading this and want to make a reprogrammable gameboy flash cartridge, then do what I did ONLY if you are quite confident in your soldering skills, you have a 32-pin DIP flash chip (and found a load of guides for using PLCC's or SOIC's and don't know what do you with your through-hole chip) and you have 30+AWG wire or copper strands with a thin laminate coating. :) Otherwise, you will be in for a lot of pain and misery.
For those of you that are true DIY drones such as myself, I can give you a few pointers here and now on how to make a DIY gameboy flash cartridge.