rangerover p38?

i have just bought a p38 and have some problems (1)the battery is only 570 amps .(2)the radio looses signal. (3)there is a fault with the srs. (4)the rear offside window does not work . i have changed the window motor and the switch assy. still no joy . i have replaced the earth clamp as this would not tighten up fully. sometimes the alarm fault comes up . thank you