Import of stock prices history from a local file

[mathe.pierre at libertysurf.fr]

I am considering switching from Quicken to GNUCash.
I am using Quicken mainly to track my stock investments, and I have a
stock price history of more than ten years for several dozen of stocks.
Questions :
1. Is it possible to import stock prices from a local file into GNUCash
( I am not willing to try to download the prices from Internet; it is 
even not feasible
as some of these stocks have disappeared further to merger/acquisitions)
2. What would be the import file format.
3. If a utility program does not exist, I am willing to write my own, 
but I need to know how the stock prices are internally stored (I suppose 
in a data base?).