These are the parts you can use. The top two are not really necessary unless you have particularly large burrs or jagged edges.
How were you planning to cut the case... as in what bit or tool were going to use. If it is the Dremel, a reinforced cutting wheel will do, but you may need 6-10 of them... no worries, they are pretty inexpensive.
Sorry, but I must say it: Please wear eye protection at the very least. IMHO I would wear long sleeves and gloves as well as some kind of breathing filter (t-shirt is great). The process creates a lot of fine metallic dust and shrapnel-like discharges...
Wavyness.... if the undulation is minor, it will not show. That is the nice thing about the self-locking gasket that comes with most (if not all) kits, it is designed to hide minor flaws.