I investigated this two years ago. Based on the investigation I decided to keep the automatic transmission -- though I'm still tempted to put in a manual. Here's what I learned.

1. The best sources of information and parts I found were based in Canada, where more drivers tolerate manual transmissions. US information sources were very sketchy.
2. Conflicting info on whether the engine computer(s) needed to be replaced. I would err on the side of caution: manual engine computers for manual transmission, automatic for automatic. Adds cost, reduces risk.
3. Manual transmissions produce more torque loads -- no torque converter to absorb them. Hence you need larger axles, perhaps stronger constant velocity joints. One info source was quite insistent about this: a customer broke his automatic axles after putting in a manual. Evidently the damage was quite ugly.
4. If you do this, replace ALL the engine mounts, since they will be under greater load. Consider polyurethane: noisier but stronger.
5. Don't forget all the interior/electrical parts and adaptions. Like the miserable ignition/brake/park shift position linkage.

I ended up with an estimate of over $1000 for items 1-3, without labor since I do my own work.

Tell us what you decide. If you make the swap, tell us what you did and how it worked out. I'm rather interested...

-- Bruce