'94 Sable issues....

Well I just got a '94 Mercury Sable as my first car in Sept. for $800.....for a couple months it worked fine...now I just had to replace a head gasket at about $1100, and the alignment was off last month:2cents: :banghead: . Now the speedometer isn't even picking up, ditto with the odometer...I need some major help because there is nobody in my family who knows about cars and I am in a state of helplessness. What could possibly be wrong with my speedometer/odometer.......:newburn: