Pumkinwheat

This is the first time using pumpkin, and second partial mash so I need advice here I will be kegging this beer as well
4 lbs pumpkin boiled take the water and use that for mashing
Follow the wheat beer recipe 3.3 lb. of Wheat Malt Extract, 2 lb. American 2-row malt, 1.5 lb. Wheat malt, 8 oz. Munich 10L, 2 oz. Hallertau pellet hops then in secondary add 1 tsp of vanilla/ nutmeg/ cinnamon / allspice

That's an interesting approach I'd not thought of - make pumpkin tea and add it to your beer rather than adding the pumpkin to the mash. Sounds like it would work for me - it has the same practical effect, the pumpkin is flavoring the water, you are just removing the pumpkin before adding the grain. Go for it!

Think the water should be boiling or 155? And think I should pre cook the pumpkin in the oven?

Bump brewing this Friday and want some help on pumpkin confirmation, as well as recipe