Changing words - animated gif

I need an animated gif with an endless loop. You will be supplied a .PSD with three layers: "Background", "Old" (at 100% opacity), and "New" at 0% opacity). This is the "initial state" in the gif. Gif sequence: 1 second: you will have it remain in the initial state 2 second: in each frame, the "old" layer opacity should slightly decrease. It starts at 100% and after 2 seconds it will be 0% opacity. At the same time, the "New" layer should slightly increase in opacity with each frame. It starts at 0% opacity and after 2 seconds it will be at 100% opacity. 0.5 second the animated gif stays in this state. Total 3.5 seconds. You will render this and then reverse it. The total runtime of the endless loop will be 7 seconds. Effect desired: Words of a parchment page "magically" change. Please make this a smooth transition The animated gif will be 5:4 aspect ratio and be 250px wide. (some 250X200) please make it as small as possible in file size without losing quality. This is a quick and simple project. My maximum budget is $30.00