Ford Escort -- short circuit?

1991 ford escort-- just bought it-- been sitting three years- jump start and drove it fine-- went to put another battery in and sparks flew--- now I have all dash board lights, and door alerts etc but nothing when I turn ignition key-- no sound of fuel injection, no sound of cylinoid activity--- nothing-- its dead air-- with a fully charged battery so blown fuse? Blown electrical system-- possible I put battery cables on backwards as nothing is marked! Signed dumb and blonde