The main idea in a pumpkin ale is that you want to shoot for a relatively low IBU (in what brewtarget would call the 'balanced' range) - select a recipe for a cream ale or a blonde or porter - and then add pumpkin and/or spices.
You don't want to use outstanding hops. Stick with noble hops and hops that are closely relative to nobles.
Canned pumpkin is a good way to go. Those Libby people know what they are doing, and conversely the grocery stores don't seem to stock what i would call a good eatin' punkin.
You will need about a pound of canned pumpkin per gallon. Since you are brewing with extract you will be adding pumpkin during the boil.
Bag your hops and plan for a lot of sediment. The pumpkin should go right into the fermenter. 6 gallon fermenter required.
Spices go in at 10 or 15 minutes before flameout. I used half a teaspoon of allspice, half a teaspoon of ginger, half a teaspoon of nutmeg, and a teaspoon of cinnamon. If you have "pumpkin pie spice" in a jar you can use 2.5 teaspoons of that. Or bump it up to a tablespoon if you like the spice.
Use a neutral yeast. Notty or S-05 fermented in the low 60's.
You may want to try fining with gelatin in the primary to get the sediment to compact further. I ended up with 4 gallons of porter and 2 gallons of trub. I had to hold the racking cane at the bottom of the beer to avoid pulling just trub. The most wonderful yummy smelling trub i have ever washed down the drain.