BN7877

Yesterday on my day off, I changed my fuel pump after noticing it had been lagging recently. However, when I took out the old pump, I noticed "brown stuff" all over the inside of the fuel tank. At first I thought it was grease or something, but when I wiped if off, it was really rough and nothing came off. Some general forums say that it's rust in the fuel tank. I plan to drop it, but my question to you guys is how do you drop a fuel tank of an 2008 Mustang V6?

Any tips while the tank is out too?