They might have installed it for you. I've never used a special tool to install one. I just press it in evenly with a large blunt tip punch and tap it gently with a body hammer. The trick is press it in evenly and don't distort the seal or scratch any surface. If you can find a can the same size as the seal that will help too. Also lube inside of the seal where it touches the crank with some engine oil. Same advice with the trans seal but lube it with some tranny fluid.
2006 Superior Blue Trailblazer SS AWD, Stock as a rock
Sold: 2002 GMC Sportside Denali front end with a 2002 LS1, FLT level 5, Yank 2600, Trick Turbo, T76, Nelson intercooler, 60LB injectors, Warbro fuel pump, Eaton locker, Magnaflow, 3.42, Nelson Performance Tuning (speed density).
Sold: 1981 GMC LB RC 1500 2002 4.8L 4L60E 12 bolt 3.73 Richmond Lock Right AC PS Nelson Performance tuning