Aloha Trish and Welcome! :wavey:
To answer your questions ... in a nutshell, Pin Pics is a database of pins. You can use it to look up pins, and if you've created an account (listed pins that you own, would like to own, and have and are willing to trade), you can use it to as a device to facilitate trades through the post.
If you're looking for a printed guide, you *can* use Tomarts, but I would advise that you take anything printed in this with at least a barrel of salt. You have to remember that Tomarts is just one opinion of what pins are worth and, really, is best used as a guideline for value and an easily portable index. However, since we're in the age of smart phones and tablets, I think looking up the pins on Pin Pics or eBay is much more reliable as Tomarts is a printed work and, consequently, inherently out of date from the time it comes out and unable to take into account value fluctuations.
Finally, as someone said, if you want to buy pins from a website other than Disney, take a look at our sale boards. However, I would strongly recommend that you always check references/feedback before purchasing and always use common sense before making any purchase or trade. If something seems too good to be true, it probably is - and never make a purchase or sale unless you are 100% comfortable with it.
Hope this helps get you started and, again, welcome! 🙂