The charcoal canister is part of the emissions system. I doubt that you would get regular shop that is willing to move the canister for you. I know we are not prepared to do it. Might be a simple thing to do but you are messing with the integrity of a fairly complex system and if it stops working as intended the shop will have a nightmare on their hands. Also adding the 2nd tank is going to be challenging in terms of the emissions system. Have a look at this site
Fuel tank regulations for some more info on installing 2nd tanks etc.