I usually save my stuff 2 times; one as a .xcf and then as png (or gif premitting)
also, before i apply a layer mask, i always save a copy of the mask before i applied it just incase i need to mess with the mask later. I just duplicate it, turn of vision for it, and move it to the bottom of the list.
To take out that part, you could use the clone/heal tool. Or even the smudge tool. All you want to do is focus on getting rid of the text and making it look as natural as possible. If you become really good at this, it can open a lot of windows of opportunity for you where you can change the picture how you want it to look (to an extent) You have to learn to find similarties among parts of the sig
