c-ron. #1 the work they did previously would not cause your evap. to leak.
#2 you'll also need to replace your receiver dryer, when you open up the a/c system you'll have to install a new dryer. And I would recommend the small line between the dryer and condenser, it is a common leaker. Since you'll be right there replacing the dryer, they shouldn't charge you to replace that small line with it.
$2900 seems a tiny bit steep but not too much. Factory evaps are really expensive.
A good independent can easily do this job, but make sure they specialize in MB.