I just did this.....Just make sure you drain the tank fully....i had about half a gallon left in the tank...and it was REALLY old gas....and the smell......
So anyway it takes about 10 minutes once you disconnect the lines drain the fuel...it is just held in by the tank strap...I removed the expansion tank first but dont know if that is required....its was just hanging there on mine...LOL
Good luck...if i did it again...id do it outside...like in the gravel.....or where you wanna kill some grass....LOL
Steve