Stea,
Being a welder myself,my opinion is that who ever you bring it to will want to do the prep and set up themselves.I would either have them tell you how they want it set up or be very specific in telling your welder what you intend on doing.you want to both be on the same page so the work gets done to your needs.make sure you bring it to someone who knows about frame welding.whatever you end up doing, good luck hope it turns out well
Greg