Great, I'm glad that you found a boat that you're excited about. At a combined weight of 300 lbs, the H16 is perfect for you and your girlfriend. I'm sure you did some research on used Hobie 16s, but I'll just give you one quick tip: beware of soft spots in the hulls. You'll typically find them on the tops of the hulls, 1-3 feet forward of the front crossbars. For $900, I'd accept a little bit of softness if everything else is ok, and there is a repair that is fairly simple and you can find directions to do it on this Forum. But, if your hulls are a bit soft, I wouldn't take them out in demanding conditions - winds over 17-18 and/or big waves can cause them to break. "Demanding" is a judgment call. For your first few days on the water, you'll want to sail in milder conditions anyway.
Getting a trailer with a registration is a nice bonus. That sail pattern is called Tequila Sunrise and was very popular in the late 70s and early 80s. It is one of, if not the most, popular sail pattern of all time. Those hulls can be buffed out to a beautiful bright yellow. Here's a video produced by Jeremy Leonard of Surf City Sailing in Santa Cruze that will walk you through the process: http://www.youtube.com/watch?v=74sEyot5A_o
Here's a link to a you tube video about tacking the Hobie 16 http://www.youtube.com/watch?v=bMka3IeyNQo
. I hope you'll find it useful. You'll inevitably have questions about rigging and sailing. Most sailors in this community will freely offer advice and be glad to help get you started on the right foot. Try to find an experienced H16 sailor to help you rig and sail, at least the first time or two.
Congratulations and enjoy the new boat.