Re: Starter Motor, easy to replace?
Sounds like the 'pre-engage' gear is not returning quick enough after starting the engine. The usual cause is dirt on the shaft.
The solenoid on top of the starter, when energized, pushes this gear into engagement with the starter ring before the starter motor turns the engine (hence pre-engage). After de-energizing, the gear should spring back out of engagement. If the shaft is mucky, the gear will be slow to return and the flywheel will spin the gear up on the way out, causing the noise.
The starter is located behind the block, just under the oil pressure switch and bolts into the bellhousing.
If you do remove and clean, only lubricate the shaft with silicon spray, not WD40.
The old question remains, having gone to the trouble of removing the motor, is it worth putting the old one back?
Personally, I'm a cheapskate and would hate to throw a good motor away, so after removing, cleaning, inspecting, lubing AND BENCH TESTING, if I was satisfied it was serviceable, I'd refit it! Cos I ain't rich!
Of course I could be totally wrong and it's just plainly knackered!