Post installation

I hope this is the right place to post this, sorry if it isn't, but I need some direction. I've been reading a lot on these forums, which are an invaluable tool, but am a little stuck.

I am implementing an e-commerce site and the drupal documentation seems to assume knowledge I don't have. That isn't necessarily the fault of the documentation, since I'd be completely lost without what is currently available. Either way, I seem to be too slow to make the required connections with the info available.

Hello. I have a question about functions in the Drupal code.

I'm in the process of customizing a Drupal site, and I'm having problems finding functions. I'll give you an example:

i just saw how the index.php is constructed. It calls 3 or 4 functions in php. What i want to know is where, in what files are those functions defined. Is there a systematic way to do this? Or do I have to browse all the files and search all of them one by one?

Thank you so much for your help.

Hello. I killed my previous site which was using the generic templates of sitestudio and then I tried Joomla for a week and couldn't get anything done...not even google adsense to work and now I am on Drupal www.thewatchworks.org. My other site is also on Drupal and I found it much much much easier to use than Joomla and Drupal was capable of doing more things right after the installation or in common terms, right out of the box.

How can I install e-commerce modules or anything related to selling?

Thanks!

Dear Sirs,
Could you please inform me what module should be used to have a possibility to make a link to a few nodes at once? For instance, there is a possibility in taxonomy module to make a link: /taxonomy/term/102,130, and is it possible to make the same link with usual nodes (story, blog entry, review)? E.g. at request of /node/11,22 there appears a title, teaser and a link for node 11 and below for node 22.

Can some body translate "read and write" CHMOD into the three figure for me?

What three numbers are exactly a "read and write" permission, so I could apply it to that file?

Thanks

I want to have the following "filtering" by user roll with taxonomy access and taxonomies

Students belong to one of two cycles (A or B). Each cycle has my classes (Algebra II, Honors Algebra II, Pre-Calculus, and Business Math).

Depending on the cycle I want different content show. Each student in Cycle A only sees content from cycle A for his/her specific class.

I have taxonomy Access module installed and created roles for each cycle and each class. Then assigned access to each class and cycle for each students.