Well,
Normally I would take the grains from the all grain recipe, and just convert the majority of the base malt (usually a pale malt) to an equivalent amount of pale extract. The conversion factor is very roughly 70% - so 10 lbs of pale malt would be about 7 lbs of pale extract.
You can then partial mash the remaining specialty grains with 1-2 pounds of pale malt (needed for mashing) and then add the extract.
If you want to email the recipe file to me I can convert it for you - I'm working on a tool to do this automatically.
Cheers!
Brad