On most machines, you do have to remove the aluminum base in order to remove the Rocker arm tappet. When you reinstall the Rocker arm tappet, put some grease on the large diameter edge and on the bottom where it contacts the rocker arm.
Yes, you can remove the #75 brass primer casting and reinstall it on the same machine. The screw with the rounded head goes on the right. When reinstalling the rocker arm, the pointier end goes under the primer punch. If you reverse it, the primer punch will protrude above the primer punch bushing.
Bruce Williams
Star Machine Works.