Information or a manual for a GP6-350

I'm working on an old Gateway GP6-350 for a customer and I'm trying to find a manual for this unit. If I can't find a manual I'm hoping someone can give me some information. The hard drive has gone out and I need to replace it. The smallest HD I've been able to find locally is a 40GB unit. The original drive was 7+ GB. I need to find out if the 40GB will work. I tried looking on the motherboard for some kind of part number to check the specifications, but there was nothing I could see without taking the board out of the case. Any help I can get is appreciated.

Jayme