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I would plan for 5 business days, but in all likelyhood it wont be that bad. I have an affected display, but honestly dont care too much about getting it fixed. I did however experience the ghosting with my original rMBP display, which was absolutely worthy of replacement.
 
I recently had my mid-2014 15" MBP screen replaced. They told me to plan for 3-4 business days, but it was ready for pickup the next day (handed in at Apple Store on Saturday afternoon, picked up on Sunday afternoon).
 
OP:

I'd suggest you do a FULL BACKUP before you turn it in for repair.

I'd also suggest that it be a bootable backup, created with either CarbonCopyCloner or SuperDuper...
 
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