what if i get caster plate? would that fix it?

 

^^^This sound about right to me. Having a caster plate adjust out what sounds like a bent frame is not the right way to go IMO.

Sounds like the front end was curbed which broke the lower control arm & bent the A-arm frame mounting collars

 

The a-arm frame mounting collars is the thing that attachs the control arms underneath the car right? Should i install new coilovers on the car first and see if the caster will fix the problem or should i go to an alignment shop and get it checked out first?

 

In either case you will need to get an alignment. Caster rarely changes unless there is play in the bushings on the front LCA. You could possibly have bent subframe but I highly doubt it. If you were running -2 camber in the front you should be clearing the fender anyway.