1999 Buick Century Relay change

Hi, I'm having a problem with the A/C on my 1999 Buick Century. The fan will blow when on high but not on any of the lower settings. I was told it is a relay. I was able to open the relay box under the hood, but not remove any of the relays. Do I need to disconnect something first or should I just try using pliers? (I was afraid to pull too hard and break something!) I found the schematic in my manual, although I'm still not sure exactly which relay runs the low fan, and there are no instructions on how to remove a relay. Also, do I need to disconnect the battery before attempting to replace a relay? Any help is greatly appreciated.
Thanks,
Tammy