I have used both an online shop (CafePress) and a local print shop. The local print shop gave me the best deal and I could see what the final product was going to look like before they were printed. I would recommend building the website yourself and using a local print shop.
Have a great day!
This is a pretty crowded market so you will need to differentiate your offering from everyone elses. All these sites are pretty much the same thing packaged in a slightly different way, so whichever you select it should not matter too much. Go with what you feel most comfortable with.
With regards to working with the graphics, get yourself a free copy of The Gimp and just practice. There are loads of tutorials on the net so if you follow a few of these you will build your experience level pretty quick. Trial and error will have you producing good graphic outputs in no time at all.
With regards to the design itself, if you are not gifted in this area, you may well struggle to make any kind of impact. As I said already it's a very crowded market you are looking at going into so the work you produce must stand out on it's own.
Consider outsourcing the design to a professional graphic designer. You should be able to get a finished design for no more than $149 ;) Be careful selecting your designer though because you want to build up a long term relationship so service will be paramount.
Anyway, let me know if you need anymore guidance.