Yes, it's pretty easy. You would keep all of the specialty grains, and then use some base malt (generally US 2-row for American style beers) in place of some of the extract. You'll want to mash as much grain as you can, so it's good to know approximately how much grain you can mash in your system.
A sort of rule of thumb guestimate is that 1 pound grain = .75 pounds LME = .6 pounds DME.
If a recipe had 10 pounds of 2-row, you could simply change it to something like this:
5 pounds 2- row
3 pounds DME (which be roughly equivalent to 5 pounds 2-row)
So, if you post the recipe we can convert it for you and show you how it's done.
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