The 545 is an older machine, but Pfaff is a very good machine. $500 is a steal.
Min/max size on the 135 X 17 needle you would use is 16 to 24. You would hardly ever use a size 16 needle, so I would say 18 would be the smallest. I use 18, 21, and 22 for almost everything.
No one lives forever, the trick is creating something that will.