you cant really "repair the fan" (Unless your a techie), what you can do is clean the fan, buy an intercooler, or play with your xbox's case open (aka take out the outer shell, though doing this would make your xbox fragile)
My uncle had all red rings (cept 1), and after just simply cleaning that melted shit on the processors, it removed them all.
also...
http://www.google.com <--- there's ALOT of guides out there for fixing RRoD. (Mainly youtube)
What I would do : [I used this method with my uncle, I can't find the guide that he used tho... btw his 360 works fine now]
Dismantle the 360 (Its way easier than you think. A T10 screwdriver or something, some small screws and nuts.. etc.. oh and a hair dryer! And lots of q-tips lol)
After you've dismantled it, get some thermal cleaner+q tips and clean off all that goop on the processor (that silverish stuff. when it's all clean you should see a nice "Intel" processor there!) btw i burned through alot of q-tips doing this... (we used like 30, lol..) When the processors are both cleaned, simply restore everything back to normal (Without those x-clamps). Oh, if you have your harddrive unplugged, do NOT connect to live, otherwise you'll get banned. so make sure its properly connected before going on live. Before reassembling it though, I would do a 'test' run to force it to get RRoD. What my uncle did was turn on the 360 (with it still open and stuff, we just plugged in the power) and use a hair dryer (on cool) to blow on the processor. After 15 minutes, if it was still green, (Which it was) we then turned off the hair dryer and let it run for another 15 minutes. (everything was disassembled, so the fan that came with the 360 was somewhere on the table) and soon enough,. the RRoD came back, (we did this on purpose, its part of the process
). If you dont get the red rings, then it's fixed, if you do, but got green with that hair dryer, its still fixed! (thats a win-win situation O.o). Put everything back together, turn up your 360, and it should be green. If not, go to google. If google phails (never!) and you still have a valid warranty, send it to microsoft.
p.s. do NOT do that towel crap. It's temporary and it can potentially fuck up your xbox even more.
None.