UPGRADE.txt needs some updating to facilitate smoother upgrades

Hi,

I'm referring to the UPGRADE.txt that lurks in the main directory of the drupal v5.1 directory.

Summary: while upgrading, following the instructions in this file (11 numbered steps) the site I was upgrading became broken and I needed to manually update the DB to be able to get back to business.

Details: The relevant site is using a custom theme which calls functions from contributed modules (including own developed module). Now, to have a smooth installation, one should first switch to the default core theme (step 4) and only later disable any contributed modules. If the administrator will first turn off modules and only later switch back to the core-theme (like I did), as soon as he/she switch off some modules that their functions are called from within the custom theme his site will get broken in some way.

Suggested resolution: The detailed upgrade steps (as detailed in UPGRADE.txt) should have two separate steps for current step #4. "the first" should be something along the lines of "Switch to a "core theme" (Bluemarine or Garland)". "the second" should be something like "Disable contributed modules.".