Addled Brain- which direction to go in setting up a t-shirt e-commerce site.Please help wise people!

Question

Hello,
I have a little experience from 10 years ago building web sites, but things have changed a lot (but i am very good at teaching myself).  Can anyone advise me on the way to go?
I want to create a t-shirt e-commerce site and have no money to pay anyone to make the site (maybe when the business is flying i will, but for now) - i am designing it myself and have all the design elements done, but do not know the best way to implement it given all the technologies out there; and do not want to go one way, to find out my efforts were wasted much later.  Here's my thinking...
The main site contains the t-shirts.  When a user clicks on a picture it takes them to a 't shirt options' page where they can configure the design (put the design on the pocket, the back or the front in the center etc).  I was going to create check boxes for them to do this which when clicked, will change the picture to show them how it looks.  This means i will create picture for every possible check box option and load that into the 'this is what you t shirt looks like' space (easy enough and i can do that i think).  I will do that for every t-shirt on the main page.
But I was thinking, could I just have a plane t-shirt in the 'this is what you t shirt looks like' space and using a picture of the design,  just reposition it and resize it using (and this is where my knoweldge is small at the moment) jqeury or some other language, or even CSS and divs?  What would be the best appraoch?  This way i would only have to create the design and the blank T-shirt and use code to position it to represent the final product.  Would it better to use a CMS such a Joomla to do this (this seems very complicated)?  Before i go any further than the design i thought i would ask you clever people.
Thanks if you got this far...
Conundrum part 2:
The user will then click proceed to checkout where i will use a shopping cart system (probably Zen cart because that is on the hosting company's server that intend to use (unless suggested otherwise)).  I will need each version of the t-shirt to have a unique product ID that relates to a database that contains pricing options and this will be sent to the 'zen cart' and that will process the transaction.  Is my understanding correct?
Many thanks for any suggestions.  Learnign one or two  things (CSS and DW) is OK, learning 5 things at once is making my head hurt! I have become confused

Answer 1

Zen cart is free.  And you get what you pay for -- software that is hard to work with, not very good, poorly supported and has many security vulnerabilities which is why hackers love to exploit it. 
Get a real shopping cart. Money well spent.  Building one yourself is risky and requires expert skill with server-security, data encryption, PHP, MySql, HTML, CSS, JavaScript, PCI compliance, SSL certificates, etc...   You'll drive yourself crazy trying to learn everything you don't know.  
UltraCart is easy to set-up and they have a free 30 day trial so you can test before you decide.  There are many PCI compliant commercial carts you can use.   If you have a merchant bank account, start with your bank to find out which gateways and processors they require you to use.  That will narrow your search to carts that work with your payment gateway.
As for your site, keep it simple, semantic, user friendly and responsive.
Nancy O.