Tip, secure the wires before cutting, when one falls inside the cap it's a bear to get out; don't ask.
Do not seal the new light base on the bottom, leave it unsealed JIC a leak later develops on top. I had a lens leaking for a long time. Dust had sealed the crack between lens and base at the bottom. This allowed water to build up in the lens, which then ran into the wiring opening in the base(base was sealed). Water then ran down the wires into the wall and rotted out the wood paneling.