Changing fan rotation on an ATI 5770

why will you want to do that... the fan cools the processor by sucking air... if u will reverse it, it will not suck the heat and throw it out. In default fan is set to cool the heat sink.

Not sure what you're asking. Some fans have a cooler that blows air through the card and out the back of the case. Others have a mid-mounted fan where part of the air goes out the case and part goes back into the case. Either way some of the air should be expelled.

There are modding kits that change the cooling, but I have never heard of anyone reversing the stock fan without serious modding (like disassembling the GPU heatsink and re-orienting the fan),