Congrats... I love mine! The auto threader is no big deal if you can thread a needle. I don't even use my auto threader. These machines like to be very clean underneath, so if you start experiencing tension problems, it's probably time to take off the foot and faceplate and give it a quick cleaning. Make sure you get the lint in the feed dogs.
If you are experiencing shoulder pain from quilting, I'd urge you to try QAYG with one quilt and see if you like it. It's really a joy to quilt just one part at a time and them join them. Much easier on your shoulders. There are several QAYG tutes in our Tutorials section here on the board.