89 ford help??

[bigred1951]

well i got a ford not a beautiful classic like the ones on here but a ford is a ford..its a 89 ford f150 shortbed..its got the engine trans and gas tank from a 82 ford f150..well the gas gauge always shows full it used to work but now it just shows full all the time..im thinking it might be a ground wire come loose or something when the bed was changed i dont know..it was done before i got the truck..and also the wipers dont work i was told it just needs the hot and ground hooked up but wiring is just not my things..so im hoping you gives can give me some advice and hints on what it is and how to fix it..thanks