Once you take the seat off, all you have to do is
1. Turn petcock to off
2. The fuel line going into the carbs connects on the left side of the bike (follow it from the petcock), it uses a little tension ring clamp to keep it on the carb. Disconnect this line.
3. On top of the bike where the seat would be, on the very rear part of the tank, there is one bolt that holds the gas tank on the bike. Undo it
4. Pull the rear part up a little bit, and then pull the tank towards the rear of the bike. It should sort of slide backwards and off.
What color are you going with? And are you going to be painting it yourself? Rattlecan or more elaborate?
I am thinking about painting mine yellow after I get her running...