Hey rickster, that's a nice looking trailer. As for your sheets, measure the bed dimensions and just buy the closest size from Walmart. Probably going to be double or twin. I have a short queen in mine which is a couple inches shorter than a regular queen but the regular sheets fit fine.
I just purchased a converter from www.bestconverter.com
and they are fantastic to deal with. If you have questions about which one you should get, call and ask for Randy and he will help you out. The Progressive Dynamics brand is about the best you can get and will take great care of your battery(s).
My truck came with the camera in the tailgate, and yes it is helpful for backing up and getting hitched on, especially on your own. I'm not sure how great the quality is in the aftermarket world though, but it's probably good enough to put the ball under the tongue. Mine even has a zoom feature and guidance lines if I want to use them. My old truck didn't have a camera, though, and I don't think I would have put forth the effort and money just to have one. It's nice but not necessary, as long as you have a helper when you hitch up.