I ordered this kit the other day and am looking forward to it. I wasn't aware of these recommendations they made... Kinda sucks.
Anyway, I brewed a brewers best spiced pumpkin porter ( or something like that) like 3 weeks ago. It had steeping grains and a spice pack. I only added half the pack of spices (at about 5 minutes left in boil) because that's what everyone here recommended. I also got a can of unspiced pumpkin puree which I baked for 30 minutes with some spices on top and added to the boil at the 15 minute mark. I just dumped it in because it would have just seeped out of any bag I had. I added Irish moss and did a secondary. I lost about .5 gallons. It's super clear, however it has a vegetablyish taste, so ill probably add pumpkin a different way next time.
I've read tons of methods for brewing with pumpkin, so i'd just experiment with whatever you feel would be easiest.
For this one I'm going to bake some fresh pumpkin(cubed) with spices and add it in a grain bag while steeping the grains. Atleast that's what I plan on right now...you don't really get much flavor from the pumpkin itself, so don't stress about it, but who wants a pumpkin beer without pumpkin!?
There is a recipe on here for thunderstruck pumpkin that I've referred to a couple times and that may help you too.
Have fun! It'll be delicious.