96 jetta

i drove my car to emssions place with out my guages working and they try to plug in thre computer but nothing is working all the fuses are good . the car still past emissions anyway but my fuel guage or temp guage is stilldown to the airbag light is on .i replaced the seed sensor when i rebuild the trans.evryting worked before exept the obdII plug . when i bougt the car preveus owners fryed the altenator so i replaced that to and do i have to take out the dash