In vim add the following in your .vimrc will help convert tabs to 4 spaces to meet part of the OpenACS coding standard.
It's also nice to have syntax highlighting by adding the following line
Also useful to use tagging features. In brief - run ctags -R in the root of the install or source tree.
At that point you can edit using vim -t procname or ::package::procname and go to the corresponding place in the code. From within the code, you can lookup functions by having the term highlighted and hit CTL-] - use CTL-T to go back.
Only works if you edit from the top directory, all tags are relative to there.