I am fairly confident that the deposition can be done on Skype, and should be done in the presence of your attorney. However, you might want to consider depending upon the hourly retainer of paying your attorney so that he can instruct and or advise you with any questions which lead down to completely different avenues.
State of mind, mental capacity, vetting process, and due diligence where as these items are used by her attorney to paint a much broader and usually negative connotation of your bud, and how he handled his affairs, family, and financials, with an apples to apples scenario of this business deal in regards to his entire life. I would confer before hand with your bud if possible as well. Just my winded two cents..................