Module development and code questions

I am wondering if it is possible to setup an SMS system where an international community could communicate back and forth with each other much like Upoc.com but only one group that sends messages.

I know that it is possible to send messages to the phone from the website, but is it possible to have the person receiving the message, reply to the group with their phone, and have their reply go to every phone associated with the group ... like a mobile messaging community.

Hello!

I want to have a "sandbox" for pages and stories where anonymous users (=user not logged in) can add, edit and delete pages and stories - but only the pages and stories they have created. The access rights should be granted based on the session id, meaning a user can only view (and subsequently edit and delete) those nodes where the node id is associated with his session id in a separate table.

If possible, the pages module should still be usable for static portions of the site.

I really would like to find a way for registered users of my Drupal site to be able to Register for events I am hosting. Not all registered users would be in every event and once they are logged in to the site, ideally it would be easy for them to register for any new events I would add.

And then I'd also like to integrate PayPal paying for those events.

I tried the event.module but it was WAY too basic for what I am looking for.

I got interested in Drupal due to this need and now that I have it installed, I am doubting that it will suit my needs.

My first patching venture, figured I might as well learn how to do my own laundry, so to speak.

I understand these:
109c110,115
76a77 and a few others,

but this one has me?
128a135,138

at line 128 ... add lines 135 through 138 ?

Anybody got a quick way to figure out if a particular module is installed and activated?

For example : lets say I would like to add a 'Add Buddy' link to the members.module member list, but only if buddylist.module is installed and configured...

Is there another module that does this that I can have a look at?
Is there a standard way of doing this?

TIA

~Tat~

I wanted to change the output of the image filter, so I edited this line that I found in the module code, but nothing has changed in the output image.assist generates. It still gives me the same format. Where shall I change the code if I wanted to add some divs and classes? Thanks!