Replacement should include

disconnecting the battery/negative cable
conducting a visual inspection of the flywheel/ring gear
removing the starter, according to service materials and manufacturer guidelines.

ASE 1: V. Electrical/Electronic Systems: C. Starting System (P-1)

Process/Skill Questions:

What should be inspected when removing a starter motor?
What is the first step in removing a starter motor?
How many wires are on a typical starter motor?
When disconnecting the battery, which cable should be disconnected first and put on last?