flex discs charge?

It is more than a one-hour job. $140 for labor doesn't sound all that bad.

It is important that they be installed correctly and that all of the screws are torqued properly. If not, you could experience an expensive failure.

I would have to look it up, but the specs also should be in one of the DIY threads.

It isn't too hard to do it. I didn't remove my transmission mount, but that would have made the front disk a lot easier. I recommend removing it.

Well, they take the place of the front and rear U-joints, but they only work with a very small angle. The Benz has a fixed rear differential, so the propeller shaft is not moving around much.

The flex disks are reinforced rubber. U-joints are hard metal and will transmit more vibration. Flex disks give you a quieter drive line.

There are two specs listed, depending on the size of the bolts used:

M10 - 40Nm
M12 - 60Nm