First they need to inspect where the lower control arms attach to the front subframe. If NO cracks are found, they will need to MIG weld in some support gussets, that's all.
IF cracks are found, then they will contact your zone office and they will authorize replacement of the subframe assembly.
A good idea at that point is to have the suspension components inspected for wear or dry-rot and have the suspension all renewed as neccesary. Anything beyond the labor to actually replace the subframe technically is at your expense. I did this once and replace the lower control arms. Since they needed to be removed and put back on the new subframe anyways, there was no additional labor charge, just the extra parts the owner had to pay for.
I really couldn't believe the whole thing. It was a 77 with over 100,000 miles on it, with a recall that should have been done in 1985, and yet MB was still honoring the recall!