I did this over the weekend after I saw the DIY here:
http://www.e90post.com/forums/showthread.php?t=740011
It was not complex, just PITA get the cap/plug broken loose. I did end up using my foot to push on the wrench.
Also, instead of cutting a Allen key, I bought an Allen socket from harbor Freight and punched the key portion out. It was the perfect length.
My car was at 75k miles and the fluid was still not bad, but a little dark.