Gearbox conversion

Hi,

I was wondering can you help me. I am in the process of buying an Automatic Defender 2.5 tdi with an Auto box. I am afraid that it is just going to be too sluggish on the auto and wanted to check on a conversion.

Firstly, can it be done? If so how much would one cost and what would the advantages/disadvantages be?

Thanks for your help,

Dave