how much would it cost to replace the front drive shafts and seals

You can find replacement front driveshafts online from $350 and up depending on which drive shaft style you have (there are 3 designs) and whether or not you have a lift kit installed. You could also swing by a performance race shop and see if they can build you one custom. Shops around me charge 375-400 to build a custom shaft for my WJ