Bring some fabric with you to do test sews. The dealer may have fabric there, but bring a sample of what you normally sew. After a demo, they should let you try any machine they have. If they don't, look for a new dealer. You should get free lesson(s). Some dealers will let you take the lessons as many times as you want, so you take the lesson when you first get your machine, then, after you use it for a while and know what to ask, take it again. I would also ask about trade ins. Often they will come with lessons and a warranty.
I personally would not buy the machine on the first visit. Take notes on the features and prices, go home and really think about what you are looking for in a new machine.