I have a Troy-bilt hydrostate, 46"cut 3 blade lawn tractore w/ a PTO blade engagement. Was cutting and the blades stopped. Everything else works fine and there is nothing hanging or loose that I can see. What do I need to look at before I take it to a shop for repair?

There's

It is an electronic PTO pull-on switch like an old headlight switch. No Lever

Check the pto switch with key on not running sitting on seat , pull the switch if no click. Check for power at the plug going to pto clutch,if power there replace clutch.
Luck