The recipe already is a partial mash (the munich malt must be mashed) that's why the instructions specifically say to use 155 degree water.
Anyway, you can certainly change the recipe if you want. It's already pretty malty-sweet. 4 pounds of munich is a bit much. I'd lose 1/2 the munich. Munich can be a bit, well, strong and malty. You can use your recipe, of course, and use less DME. I like the original, though.