starter and power locks

hey

my name is alex and i have a 91 explorer 4x4 xlt that i jsut bought.. we got it cheap and it has minor problems that i need advice fixing... for one the starter cranks the motor when it wants and i just bought a starter and the new starter doesnt crank at all... i noticed that the small read wire going into the starter is filthy so im going to replace that and see if that fixes it... i also think that there might be a draw somewere cuz the battery light is always on.. also only half the power locks work so i need help with that

any help is very appreciated

thanks,

saylor