I was very scared to begin machine quilting too.. I don't have enough money to buy 20 yards of muslin and batting to make "practice" samples from.. I think that would be a great way to get up to speed, and those smaller baby size sandwiches could be used for other things.. I have one that I use as a changing pad..
What I did was take home some of the kits we have at our guild and practice on these donation quilts. You will be surprised how quickly you get better at running your machine at a constant speed. It just takes practice like everything else. The best thing to remember is stop when you aren't sure where to go next or just get cluched up.
As far as the back side.. I spray baste my quilts and don't have that problem. The other thing that help that some is to have a slippery surface under your quilt.. I use one of those cheapy oven liners that I've cut a rectangle out of so my needle area is visible.
And, remember, this is a quilt, not a live changing project that will be displayed forever and judged.. Relax. It will look better than you thought when you finish.