rubis

Hi everyone, this is my first time at posting on here, although I have been reading it for some time, and I need a bit of advice. I have just bought a Trace Elliot BLX130, which is in need of a little bit of work to get it up to scratch, the main problem being the input gain potentiometer which has disintegrated inside and has a snapped shaft............its definately Donald! The markings on the pot are 50KB and 325a and it has three terminals. Firstly is the 325a significant in getting a replacement? Could I go along to somewhere like Maplins and ask for a 50KB pot and would I get the correct one, or do I need to be asking for something in particlular? thanks in advance H