I would definitely suggest seeing an orthopedic vet for a second opinion. ACL replacement in a dog that weighs more than about 50 lbs has a very high rate of failure, and subsequent examinations could have been affected if there were any inflammation, giving the impression of stability. Did the vet do an MRI to make sure the suture itself is holding?
From what I've read about damage to the meniscus, although it doesn't technically 'heal' itself, scar tissue forms and will eventually take on the characteristics of the meniscus - although that process takes years. Everything I've read agrees that you need to leave as much meniscus as possible but that many vets practice the "when in doubt, cut it out" philosophy.
I would suggest that you look for a veterinary teaching hospital for your second opinion. The teaching hospitals are good because you get a whole team of folks working on your dogs case and they normally have the best equipment.
Livin in a Newfie Drool Zone