How do I load android 2.3.4 onto my dev phone?
One option (probably the easiest) would be to install CyanogenMod on your phone. I don't recall offhand if the latest stable release (7.0.3) is based on 2.3.4 or 2.3.3, but you could certainly use a nightly build instead which would be 2.3.4. The forums for the Droid can be found here, and they have a section for stable builds and a section for nightly builds that you can take a look at.

For detailed instructions on how to prepare and install CyanogenMod, the best resource is their wiki page.