there are plenty of posts on the rad 9800 pro to xt flash, but ill just give u a rough outline of what i did.
Take off the heatsink and fan, then use a bit of tissue paper (good quality) and wipe the thermal pad off of the core, read wether it is a r360 or r350, if its a r360 then you can flash it to XT, if its r350 u cant. if u do have a r350 core do not worry tho, as flashing to xt only gives u slightly improved shaders and about an extra 100 points in 3dmark 03, and r350's are generally better overclockers that r360's.
Next read the memory chips around the core, it will either says hynix or samsung, then u are clued up.
Buy urself a decent hs, maybe the HIS comes with the arctic cooler already, not sure, but if it doesnt buy one and use a thin layer of ac5 to cover the core (about 0.5 mm think), remount the HS, making sure HS and core are in contact.
Next just go to the ati overclocking page in this forum and look at the "How to softmod ur 9800NP, 9800 Pro into XT" thread, then ur sorted