2000 Jaguar S-Type auto gearbox

lumpy & jerky getting into reverse also under normal driving conditions gearbox fualt light comes on and then it wont go into top gear so i have to stop & turn engine off,it then resets itself once engine has been restarted but will come on again later on & then you repeat process.noticed also whilst in drive & stationary with foot on brake there is a funny noise from gearbox like a growling noise is the only way i can describe it.my mechanic has changed transmision fluid & refilled with jaguar recomended fluid also new filter & cleaned of the magnet but still the fualt persists.the diagnostics is giving four fault codes po734,po735,po745,po795.my mechanic has sinced drained the fluid & checked that he hadn't disturbed any wiring close to filter as someone had told him that this sometimes happens, refilled it but the problem still exists will i have to replace gearbox & if so will a second hand box of same year & model need reprograming to computer or can it simply be fitted & plugged in.