S3 replacement Gearbox

Hi,

My gearbox has finally decided to give up by removing 3 teeth from the third gear on the main shaft. Is it a hard job to replace the main shaft and third gear on the lay shaft, providing I can get the parts? Or can anyone recommend a supplier of replacement or exchange gearboxes. Is there anywhere in the North East that could help?

Thanks

Liam Series 3 SWB V8 liamhoskin at blueyonder co uk