If you need the space, then it's worth it....
Don't know how it affects resale, but I wouldn't imagine that it would be a negative figure as more seating is good for the general public.
You may have trouble finding a shop that will accept the possible liability concerns of cutting out the deck. I do them here but I get a waiver signed.
I have done a few for the local upholstery shops, and have charged $1200-$2000 for cutting the hole and adding supports as necessary. I have no clue what the upholstery shops charge for their end, though. I would guess somewhere around $2000 for quality work. If you need a referral feel free to give me a call.