I have the PE770 too and I like it a lot. I bought mine from Amazon. I was worried about buying a machine like that online but it was perfectly adjusted and ready to stitch right out of the box. I've had no troubles with it at all. It can handle larger hoops but I mostly use the 5x7.
The USB stick I use in my machine is a cheap unbranded one that I got for free as shwag from a vendor at a work event, works just fine!
I do think classes would be valuable - I read a lot online but I still screw up and use the wrong stabilizer, etc. I kind of have to fumble around a bit before I get it right sometimes, which wastes materials. I could probably find local classes to take - I might look into that after the holiday and year-end chaos subsides.