Replacing '94 Altima Serp Belt

I have a '94 Altima with 112,000 miles. At the recommendation of a few people, including the mechanics that routinely change my oil, I recently had the original serp belt replaced. My oil changing mechanics said they couldn't change the belt because they said something about the belt going around some engine parts that they couldn't work around. So I took my car to a local automotive chain to have the work done. After I picked up my car, I noticed that my heater was not working. It was working when I took it in, given that the morning was pretty chilly. The next day, my car started to overheat and it did so very quickly. I've called the place that did the work and they tell me to bring it back in so they can take a look. I would just like to see if anyone on this board has knowledge of replacing the serp belt and if it is possible for someone to damage the cooling system during replacement.

Thanks,
Steve

I just changed the belts on my '96 Altima. 2 Belts. The A/C compressor belt has to be removed to get to the serpentine. The cowl under the right side front bumper has to be removed to do the job, and it is difficult to get the serp belt off and on. The serp belt powers the water pump, alt, and power steering. It sounds like the water pump is not being powered by the serp belt.