In the last couple of years I have changed out the inserts on both of our 1994 940t sedans. I had the luxury of taking all the time I wanted so I didn't keep track of how long it took. If I were to guess I think you might be able to complete the job in that four hour time if none of the fasteners gave you any trouble, but my guess is they will.

On the first pair I could not budge the gland nuts. I took them to my machinist and he used an air hammer to get them loose. On the second pair I used PB Blaster on the nuts for almost a week. Between applications I tapped with a hammer to set up vibrations in hopes of increasing the "creep" of the penetrant. Occasionally I used a torch to warm things up with Mapp gas. After days of these actions I used a brass drift and heavy hammer to break the nuts loose. It is not fun work but it is satisfying.

So the bottom line is that those nuts are going to be the unknown factor in how long the job will take.

Good luck with your efforts,
Randy

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Any twenty minute job is just a broken bolt away from a three day ordeal