Crank Shaft Seal - Oil Leak?

Long story short my truck is in the shop due to an oil leak and the mechanic says it's common for the crank shaft seal to break and wants me to replace it. That's a $1200 fix! Have any of you ever even heard of this issue?
Right now he blowed out and cleaned the pan, took the truck on a test drive, left it running a little while, no leak yet.
Current plan is to go pick it up and see what happens over the next few days

 

Yes its called a rear main seal and it is a common part to go bad.

 

$1200????? Damn.
If he was having to do it at night in the dirt in 105 degrees with 95% humidity while getting stung by fireants with only basic hand tools and maybe a floor jack and had to be done in 12hrs......maybe $1000. I would do it for $600.

 

yeah 1200 is pretty steep.... it's usually pretty easy to do if you have a tranny jack id say keep looking for a mechanic.