abs sensor fault

hi there, was looking for a bit of help regarding my brothers E91 2006 320d. He has a fault with his abs/dsc. It has a fault code  5E20 saying that the hyd unit pressure sensor is faulty. Apparently this is housed internaly in the hyd block. Bmw say you need to change the block at a cost of £2k but he has sourced a new pressure sensor from somewhere. He wants to know firstly if he needs to diconnect the battery before unplugging the abs hyd block. Also when he fits the new sensor, which apparently is built in to a circuit board, will it have to be coded to the car? Also if it does need coded, will the car still start before the coding has been done? He says he has a prgram called v32 and he can code it himself if need he needs to but its saying his controllers software needs updated first. Sorry for the long post :) would be gratefull for any help, thanks