can you sew zippers? I need help, will pay $50

My dryer went completely nuts and ripped off the zippers for FOUR of my favorite hoodies. I'm extremely bummed about this, and furthermore, the local alterations store wants to charge me $25 each to fix them (the zippers need replacing). I have a sewing machine and very basic skills (I can do my own hemming & small fixes), but I'd like someone to help me/teach me how to replace zippers, as I've never done it before and I'm afraid of ruining my favorite hoodies.

My budget is for a total of two hours of help, so $50 for the project and it can be done at my home in Mountain View or your place if it's nearby (e.g. campus, Menlo Park, etc.).

Timing is flexible.

Thanks!
Lindsay