The answer to this is to contact the solicitor who made the will and ask them what they may charge in order to make any changes to it, you can also ask them how long it would take.
I would say that it wont take too long, but the cost is down to the solicitor themselves, so that would be your first port of call.
Hope that helps and good luck with this one. :-)
Jo x
For more info on how i have come through bankruptcy and for links to help, you can read my blog here called: Needafriend's Info on Bankruptcy :-) http://debtfreejo.blogs.bankruptcyhelp.org.uk/ Needafriend says: Live life to the full, take life by the horns and live a little, otherwise life would be so boring!