rear main seal repair

I caved and took my Mustang to the shop. There was a persistent leak as I've described in previous posts, off the back of the engine to the front of the trans. I suspected the rear main seal, but I don't have the capability to replace it at home. Shop confirm that the rear main seal is the source of the leak.

Two questions... repair is about $850. Does this sound reasonable? Includes full rubber rear main seal and full rubber oil pan gasket.

Also, they are saying rear main seals can go out from routine driving. That doesn't sound right. I've never replaced one in any car I've owned. What do you guys think?

Sounds like they want to pull the engine. Get a second opinion cause it can be done without pulling the engine.
Make sure the shop doing the work rotates the seal for a parting line of 10:00-4:00 o'clock.

$850 is not far out of line really it's maybe a little much but they are probably doing a little CYA in the estimate. There's a lot of labor in replacing a rear main. @ $60-90/hr it adds up real quick. That's why it's a great thing to do yourself if you can. It isn't that complicated but it takes some work. As for why it leaked? You won't know until you look at it as it comes apart and even then it may not be apparent. All you can do is replace it properly and pray. Know how it's supposed to be done before you break into it. If you can do it yourself it will cost you $20 and an afternoon or two. You may have to lift the engine off the mounts to get the oil pan off I don't know. I've only done two in place, one on a huge ford lehman in a boat, it was a bitch, I'm sure it will be easier on a falcon or mustang. On the other, I do know we had to lift/hang the engine off the mounts to pull the oil pan out of the way(b/c of the oil pickup) on a 65 econoline 170 for a piston replacement on #6. Tried everything under the sun for a minute to get that pan out or get to the oil pump bolts. It was a good thing to b/c one of the mounts was completely delaminated and the steel was just laying on the rubber on that side. So we replaced the mounts while we were at it. We wouldn't have noticed otherwise. That rig is, believe it or not, travelling as a daily driver in the Netherlands. Into the city on a regular basis 8)