Define your level of "DIY"...
An opti swap is really not that bad, there are quite a few writeups on it, and no, no timing changes are done.
Hardest part would be the hub removal from the crank, but again, do some online research and take your time, tis straightforward.
Heres one quick link..
http://shbox.com/ci/cam_removal.html
Granted you won't be doing a cam swap, but scroll down, opti R/R is covered.