It will need overhauling regardless of storage conditions, last one I saw that was a core for overhaul, I.E had been remvoed from an aircraft time ex and was being offered for £17,000 on ebay with no takers...... looked but the link is dead... Do you know what it is exactly mark and model, the merlin is about 1/2 the size of a Griffon, I could find out for you if you want as I have friends maintain one.
Incidentally if you do have one see
http://answers.yahoo.com/question/in...9215247AAjUL9z
bear in mind the prices here are quoted in 2005... see link below
http://forum.keypublishing.co.uk/sho...stpost&t=50487