Rear arch rot repair

Hi I have got alot of repair work to do on my offside rear arch there is a rusted area at the top forming a 2 inch hole where it connects to the door pillar but the worst is behind the pillar where the arch meets the the rear wing a good 6 buy 4inch hole has anyone had to tackle this if so whats the best method, is there away of pulling the wing away to get in to repair or do you leave it in place I am not to bad with a mig welder and an ark but havent done any with a tig I would be gratefull for any help or pictures of repair methods thanks