Removing Thermal Pad on an AMD GS [arctic silver 5] [thermal pad]

Q: I heard that isopropyl rubbing alcohol use for the thermal stuff that came on the floor of my heatsink removal. I will be applying Arctic Silver 5, but before I do I would like to know how much I have to clean the heatsink? I have removed nearly all traces of the heat things, but if I keep at certain angles, I see the outlines of where the thermal pad was. means that there are traces of thermal stuff left and I have to clean?
if not how much tolerance there is for the old thermal stuff

Heatsink / fan, what kind of connection? [thermal pad] [heatsink fan]

Q: Is it necessary to use thermal compound or grease or a thermal pad when attaching a heatsink / fan on a socket A 800 TBIRD?

I have none of that, just wondering if it is needed or if its just something extra?