Hi,
went through this exact same senero with my 91' 300e about a month ago.
First there seems to be 2 different elements available, mine was a round black canister about 2x2 or about the size af a tennis ball, with the release handle out the end.
Mine had 1 plastic tab located forward on the centerline shaft, (forward of the canister at about the 1:00 possion) I just pushed
inward as hard as possable with my finger tips and pulled directly rearward fairly hard and the canister just poped loose with no damage.
Ordered a new one from Phil right here at fastline, like 35.00.
Just be sure it's in the unlocked possion when you remove it, i think it matters??, I think I removed the vacuum line before i pulled the canister too.
it is replaced by just pushing it back into place, the plastic tabs just lock back together similar to an electrical connector.
Best money I spent, now my vacuum pump only runs 2 or three seconds per lock or unlock, before it a good 20 seconds and the fuel door would not lock,
The diafram had a small tear in it, old age I guess.
Best of Luck!!!, It was Easy!!!
JOHNV

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1991 300e 255K (14.62mpg)
1979 Corvette L82 (sold)
2000 Custom Harley Sporty 1200
(Ride Hard or Stay Home!!!).
1973 Dodge Charger 440 (sold)