Hi Jim,
Yes, you can ad a BIN or change the listing anyway you would like until there are bids. Just go to the edit listing link on your ad and make the changes.
Even after there are bids you can make some changes but, in some cases you must notify the bidders. There is a good explanation of all of this on the Seller Tools section. If you don't know where that is do a 'search' on those words.
That you ask this question is kind of ironic because about 3 hours ago I emailed a seller concerning a listing for a Gibson guitar I have been watching. I asked him if he would be willing to ad a BIN to his listing for his opening bid price. He agreed, and 5 minutes later I believe I may have made the buy of a lifetime. 
Won't know for sure till it get's here but, it sure looks good.
Jim[This message was edited by Jim Landers on 21 December 2006 at 09:57 PM.]
