I'm glad your STDs went over well! Now, as for the real invitation. I know a lot of ladies are sending thiers out about 4 months in advance. That will allow you plenty of time for them to RSVP so you can do such projects as OOT bags if you'd like. So, that means that it's a good time to purchase invitations. From what I've read and what I've designed, there are a bunch of things you CAN include in an invite. First off, accomodations, travel agent information, wedding website information, welcome dinner info, RSVP to wedding and to AHR (if applicable) and a AHR card. Obviously, you don't need to include all of these things.
If you are going to make your own, there are many designs that are very simple for the "noncrafty" person, and then there are some more difficult ideas. It depends what kind of a look you are going for.
Let me know if you have any questions or need any suggestions