Good on ya. 20hrs is more than reasonable if you aren't a long time wrencher. The job can be done in under 7 hrs for one person once you've done it a couple of times. I personally wouldn't change out either the O2's or the EGT's. I would also look to swap out the two large O-rings for the coolant bypass pipe simply because they are only a few dollars and easy to swap both out in 5 minutes while you have full acces to the rear of the engine. Finally, I would would pop off the voltage regulator for the starter and confirm what the wear is on the stator. Likely doing just fine. Up to you if the additoinal $75-80 for a new regulator is worth it while you have easier access to the alternator. Replacing a bunch of items can quickly get the better of you time and money wise.

The removal of the 5Tip for the 6MT will improve your ability to access both from below without having to remove the engine in the future should the need arise (will just need to lower cradle a bit) as you have improved clearance around a smaller belhousing. The one thing I would however recommend you do while you have this out is to relocate/replace your Suction Jet Pump (SJP) like I did recently.

http://www.rs6.com/showthread.php/32...ugh-idle/page2

Enjoy.