Are bearings and the voltage regulator the only things that wear in these alternators? Windings and diodes aren’t on a clock?

I’d get at least a 90 amp alternator if you have or plan to upgrade to an afterglow relay.

Sixto
98 E320s sedan and wagon

Get the bolt on type, and its harness from the junkyard donor.

If you are upgrading the amps, you don't want the wimpy spade connector wires.
Over time the spade plugs tend to get unplugged from the alternator due to engine vibration.
You can drain your battery down if this occurs.

With 'Rena 2.0' I had long standing intermittent charging problems that were finally cured with a replacement junkyard alternator harness.
A cigarette lighter voltmeter helped to monitor voltage and charging status while driving, prior to the fix.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I thought the front bearings would be a nightmare, luckily a bearing shop isn't too far from where I live.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Dremel tool. Cut-off wheel. Chisel.

Cut off outer race. Cut half way through inner race. Crack it with a chisel.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

I've not found a Youtube video on this subject that illustrates an acceptable method for removing the front bearing. All of them use things like vices and die grinders to destroy the bearing. This inevitably does violence to the soft shaft or the spacer, neither of which are replaceable. The best method I've found is to use a clamshell puller and crossbar to take the retainer, bearing and spacer all at once, as in this illustration from the Porsche side of Pelican:

http://forums.pelicanparts.com/uploads20/11341332635.jpg

Done this way, the only damage might be a slightly bent retainer, which is easy to straighten, or replace in the worst case.

The diodes may degrade slowly over time, but a more important factor would be transient overloads which can burn them out quickly. If the diodes test ok, they'll probably continue to function for a good while unless something else goes wrong in the electrical system.

Windings are another matter. The main culprits are centrifugal forces and heat. The weak spots in the vintage Bosch AL65 are the two wires that connect the windings to the slip rings. These wires trail across the outside of the rotor, and are prevented from flying loose by nothing more than an epoxy coating. Sloppy rebuilders don't pay attention to the condition of the epoxy, which should ideally be reapplied and oven cured when the slip rings are replaced. I discovered this pitfall after replacing three rebuilt alternators in a row.

Do you know the sizes off hand? I just realized they're a few bearing shops around me, and I'd MUCH rather replace the bearing than buy a brand new alternator.

I would like to get it ahead of time since my 300SDL is my only mode of transportation.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

How much do the clamshell puller and cross bar go far?

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.