1) perlsec, and other cgi/web security information.. sorry, i don't have a specific list offhand.
2) you say "the calendar is similar to this one", does that mean that the calendar code is already written? if so, then just writing an app to edit specific table info shouldn't be too hard at all.. and for the most part, it may posibly be small enough that it doesn't matter if you reinvent the wheel. But some things to look into might be some of the templating modules.
3) I don't think you give quite enough info to answer this. Again, if you're just editing specific table info, then nah, it should be a fun task. If you need to write the whole script.. well you've got quite a task ahead of you then...
good luck,
-Syn0