If you can, test the machine run it and see what the stitches look like and check to see if there are any "odd" sounds. The number of stitches would not bother me. Personally I would be more concerned with the ProStitcher tablet. You need to be sure that is runs and can complete a row without an error. You might ask which tablet they have and how old it is. You can call HQ directly (their techs are fantastic to talk to) if there is not a dealer nearby and ask if the tablet is updatable.
Yes HQ has videos as to how to use the longarm as well as the prostitcher if there is not a local dealer. Some are good and some are so so.There are several excellent outside sources for training as well. There is a gal who does online classes (MK Quilts - her main page and MK Quilt University - her online classes) as well as a fantastic supportive group ProSiticher Possee on FB.
Good luck on your choice!!