It's relatively easy since you have a cab tractor. Cab tractors come with the internal gear, so all you need is to purchase Order Code: L8338 Mid PTO kit All Grand L-40 Series. It costs $377 according to my older 2016 price sheet.
This Order Code is ordered through Wholegoods or the sales department NOT the Parts Department. It should be a complete kit (mid pto, lever, etc...)
Of course you'll need to drain the hydraulic fluid to install.
Very simple bolt on. I did it on my Grand L30 series tractor and they are designed similarly with respect to the mid PTO.
Good luck and let us know how the conversion goes.