It works pretty much the same as any third party sale. You need to draw up a contract and submit it to Disney for a ROFR waiver. You can call member administration to ask about the process for submitting to the ROFR process.
Depending on how close you are to this friend and how trustworthy they are you can either (a) file the deed yourself and save a bunch of money or (b) hire a closing company to do it for you, do the title search, title insurance, and the closing and spend some more money.
Only you can decide what you want to do and what your friend feels comfortable doing. Doing it yourself is a little complicated but not too difficult, especially if your friend bought direct and there is no mortgage on the deed. If there is a mortgage that needs to be paid in full before Disney will allow the sale. If your friend bought resale you might want to spend the extra few bucks on a title search, just to make sure everything is kosher.
If you do it yourself you need to decide to use a warranty deed or quit claim deed - different protections for seller and buyer on each. I am going through this process now (but with a gratuitous transfer) but the process is the same so let me know if you have any questions.
