WingNut60;
I've never replaced pickle forks but can tell you that when replacing major structure members it is not uncommon to require shoring and/or pre-loading of the fuselage and/or wings..
If all the parts and tooling are available with skilled structure mechanics 3 weeks is not unreasonable.
Another issue is that once an area is opened up for repair other issues can arise such as corrosion or cracks and that has to be addressed also. That has the potential to add repair time to the aircraft.