As far as the names go, Disney does most of their customizeable shirts through Zazzle. They have a whole list of names available so you can find yours, and from what I remember when I made my grandmother a Donald shirt, if your name is not listed you can request that it be added to their list, however they'd only add real girls and boys names not vmk names. You can get all kinds of Disney shirts there, some of them have select phrases you can use depending on what character the image is for. I know for a lot of their other shirts they have all sorts of sizes, styles, and colors available. It's a cool site, I'm not trying to advertise for it or anything - lol, but it's great when it's hard to find certain characters on t-shirts, especially adults who like princesses.
I love that they decided to make VMK shirts but I wish they had some better graphic options other than all the cute or boot. I'm liking the ones with the ice though. If I do get one, an ice cube will have to be present. I heart ice.
As far as making your own shirts with iron on transfers, although there are tons of programs out there, all you really need is the transfer printer paper. I know HP sells some and I've used it before and it works great. You'll have to have to make a mirror image of it on your computer so it comes out right. If you need any help with it let me know. Photoshop is my friend.