Jeff
Re-trimming is an expensive job whatever material is chosen and it depends how extensive the job is. Obviously seats only is cheaper than seats plus all other cabin trim, but a bad job looks terrible. The range is probably £1,000 £1,500 plus materials for a car interior i.e. seats door panels rear panel and roof trim. I am getting my Monte re-trimmed for the Monte Consortium Turin trip and I have had epic problems with the supply of appropriate fabric because I do NOT want a leather interior. I have found a very skilled trimmer in Boune End, bucks but I have had to postpone due to fabric suppliers letting me down. My advice is focus hard on the materials you need and get samples as quick as possible and check the situation on stock and delivery.
Good Luck
Eric