new guy need help

hey guys. i just bought my frist car . 1989 toyota supra 7MGTE. the engin was rebuilt with upgraded head gaskets, turbo is boosted to 12psi, full 2.5 exhust. it wouldn't start tell i replaced the already new battery which was corraded with the green death corrosion. it had a hard time firing the frist time. then it was fine. it seams to be lacking power though. although i have never driven a supra before. i think it should pull hatrder that my buddys civic with b16. problems: the odometer and dash light not working. rpm does and all the warning lights work too.the coolent light is always on and the temp gauge jumps fome nothing to full. oil leak to spots near front of engin. BAD doesnt seam to be the head gasket, more near the cam shaft case. is it that gasket? and is it easy to rplace. as well can does anyone havew any advice about fixing the rear rocker panels. smalll rust holes in wheel well above rear wheels