Can you measure caster at home? If you can then it is labor intensive, if not a good alignment shop or body shop is needed. You really need to get the caster right or you will fight the car. Example: my BSI weld in plates (16V Golf) took 12 hours to install with a alignment machine and a MIG. I ended up with exactly 4 deg positive caster on both sides and it has stayed that way for five years of racing.
Jon