Starter replacement?

Electrical problem
1992 Buick Lesabre 6 cyl Front Wheel Drive Automatic

Where is the starter located on my car

I replaced the starter on a 3.8 L "C" 8 months ago using the original GM shim on an after market starter from Auto Zone. That starter is now junk as the nose cone has broken off and A Z has replaced it under warranty but that begins my concern. A Z says that can be caused by improper shiming or the part was dropped. I know it was not dropped while in my pocession so I am thinking shimming could be an issue. The replacement starter comes with 3 shims which if you put them together are not as thick as the original GM shim I used. So if I would use the thinner ones the pinion gear would be closer (less clearance) to the flywheel than the thicker one which will drive the gear down away from the flywheel so would I not want to use the original shim? Also the instructions for the replacement says to check the clearance by removing the flywheel inspection cover but I am not sure (at least I do not see one) on this engine. Is there one and I am just not seeing it laying on the ground.

I recently bought a starter and solenoid replacement for my 1988 Buick LeSabre 6 cylinder 4 door front wheel drive. The old one that I took off did not have any shim to connect to the teeth to actually start the car so when I replaced them I did not use the shims that came with the new starter and solenoid thinking I did not need them but I think that I do because it will not engage with the teeth. My question is: How do I use the shims, where do I place them? They came with 3 shims and a small little rod (the little rod is about 3 inches long and a little thicker than a wire clothes hanger). What is that little rod used for, how many of the shims do I need to use and how do I know if I have it shimed correctly? Please be as detailed as you can. I have a Chilton Manual but it doesn't really mention anything about the shims. Thank you so much for your help in this repair issue. You can email me a response at robert5621@att. Net. Again, I really appreciate it. I would make a donation, but I am on disability and have no job. That is why I do all the repairs on my car myself. Because I can not afford to take it to get fixed. Also, is there anything else I need to check as far as the starter and solenoid are concerned? Thanks for the reply. In the answer, you said to use half of a shim on one side or the other. Does this mean that I should cut the shim in half and use the little rod to measure the distance from the starter to the teeth on the fly wheel? Also, does it matter what side I put the shim on? Any and all information you can give me would be very helpful. Maybe even step by step, so I can make sure I do it right. You can email me the additional information, that would be great. Thanks again!

Have a good day,
Mike Thompson