When I converted it to all extract, I didn't like the results. The specialty grain bill has too many "must mash" ingredients that don't convert well to an extract recipe.
If you can't do a full 6.5 gallon boil, stop reading here. Otherwise, the following instructions are a rough guess based on the beer style and minimal brew equipment:
Heat 5 quarts of water to 167° F in a kettle big enough to hold the water plus all of the grain (loosely held in a grain bag). When the water is up to temperature, turn the heat off, and add the grain. Move the grain bag around a bit to fully soak all of the grain, then measure the temperature. You are shooting for about 155° for 40 minutes. Slightly lower temps are ok, but don't go higher. You can directly heat the mash if you undershoot the initial temp.
After 40 minutes, assume that conversion is complete, and sparge. The easiest way to do that is to remove the grain bag from the mash water and put it into a large colander. Pour the mash water into the boil kettle, and heat another 5-10 quarts of water to 170° F. Hold the colander over the boil kettle and slowly pour the sparge water over it, rinsing any residual sugars from the grain.
Top the boil kettle up to about 6.25 gallons, add the extract, stirring well, and proceed with the boil just as you would for an all extract brew.