No Athlon will work with an Intel chipset. The Athlon (which is Slot-A by the way, not Slot-1 like the PII/III) will need a Slot-A motherboard with either the AMD-750 chipset or the Via KX133. Those are your only options.
Ive been using Ebay for 4 years and never had a problem. Ive bought alot of computer stuff there. Just remember to check the sellers ratings. I usually wont buy from anyone who has less than 100%. Alos check the shipping charges. Some people charge alot to make up for the low selling price.