No real need to get it done at a workshop but you will need a rattle gun to undo the bolt as there is no real means of preventing the shaft from turning other than putting a strap on the flywheel or removing a spark plug and fitting a piston stop
I for one gave up tensioning then to exact specs ages ago
I just set the gun to it's lowest setting and tighten till the head stops turning with repeated applications
Apply some copper anti sieze (seize) to the PTO shaft so it comes off easier in the future as they get very hot in use and corrode tight on the PTO shaft
And do not stick your head directly underneath it because it won't budge, then it will come off in a rush & leave a sizeable divot in your forehead ( if you are lucky ) or even break your nose .
If it won't budge put a bearing seperator (separator) behind the top of the unit then a 2 jaw puller on the bearing separator
Do not try to lever it off as there in not enough room and you will end up bending the drive pulley ( more $$$$ ).