We can have a crack at it Gyro. The more info you can give on your original recipe the better.
The calculator/BIABAcus 1.0 I'm finishing up now will help with this as it will handle extract and sugar potentials and colour (if you know them). Unfortunately, this is the last bit I have to write and I'm not sure how long it will take.
Chuck your recipe up though and I'm sure we can get you sorted.
(I'm not too sure how well extract converts to all-grain as I'd say a lot has to do with the integrity of your extract in the first place. For example, one of the best lagers
I have tasted actuaaly was an extract kit for an IPA