I'm sure there are several contributors to this forum who already run ticketing web sites. One option would be to look for sites on the net that do what you want to do using php (just look for a PHP component in the URLs) and then get in touch with the webmaster to see if s/he would be willing to help. You could offer to place advertising and links to the other site on your own site as an incentive.
Bearing in mind that I'm also a newbie, I'd suggest you need a database (MySQL), some HTML forms which update the database (protected against mailicious code using some simple PHP functions), a checking system so that the same ticket is not sold twice (MySQL routine plus session tracking or thread protection to avoid simultaneous double purchase of the same ticket), either a credit-card payment system or a billing system (if you do paper billing, you could do it through PHP-generated PDFs, you then need some automated way of finding out whether someone has paid before you mail out the tickets), a system for informing visitors which tickets are still available etc., etc. If you require addresses, credit-card details etc, you'll need to look into SSL (Apache with SSL) as well since no-one in their right minds will enter address and/or credit-card details without some security guarantees. You can probably keep it all very simple, but make sure you protect your finances, your database and your website, since money-making enterprises often attract the attention of bored script-kiddies and crackers.
You can do all this yourself using open-source software, but get ready for some concentrated study and testing phases. You need a solid PHP/MySQL primer (Wrox, SAMS, New Riders, O'Reilly ...) and, if you're planning to host the site on your own computer as opposed to at a commercial hoster, you'd better read up about Apache (with SSL) as well.
If you want a complete script and file system ready made for your own website, you'll probably have to pay. There are a lot of very generous people in this forum, but a custom-built script and database system for your website is something you would have to pay for (possibly quite cheap, though).
Right, I'm now handing this thread over to the experienced and competent people at this forum and wishing you the best of luck.
Norman