throttle cable 1994 nissan

how hard of a job is it to replace the throttle cable in a 1994 nissan sentra xe (ga16de). My throttle cable is falling apart, and I don't have the money to pay someone to do it for me, so I'm going to buy the throttle cable and do it myself. Can anyone tel me how? Does it involve messing with my firewall at all? Right now my car is stranded in the parking lot of Sheetz, so I need to change the throttle cable fast, and without a lot of hassle. Thanks