You can do this if you dont want to pay for all that other stuff.
The stock fire grate let to much charcoal fall through so I covered it with a piece of 3/4x9 expanded.
Made a ring to hold some charcoal for low-n-slo. Along with some 6" long pieces around the outside of the charcoal to allow more air under the charcoal and help let the ashes fall through. The inside ring is 4" high and about 15" wide. This set up will allow the kettle to bbq for 12+ hours, at 225*, with homemade oak lump charcoal. It will burn longer with briquetts but I havent tested it with them yet.
A new cooking grate.
A couple fattys I cooked while I was doing a test burn. The charcoal wouldnt burn consistantly without the pieces of expaned metal around the outside of the charcoal but it worked good enough to cook a couple fattys.
Heres a butt I cooked after I got the kettle tuned up and running nicely. If I remember correctly the butt had been cooking for around 7 hours in this picture.