1 - 128x128: https://cache.toribash.com/forum/tori...lates/head.jpg
256x256: https://cache.toribash.com/forum/tori...lates/head.jpg
512x512: https://cache.toribash.com/forum/tori...s/512/head.png
Save it to your desktop then on Gimp, just go to File > Open and click on one of the templates.
2 - I only know how to bend lines on Paint and I think is easier.
Open MS Paint, press Ctrl+A to open a new file, click on one the templates.
Then in shapes, there's a curvy line. Press it and make one straight line with the length you wish. Then you can modify the line as you want to make it curvy.
3 - There's a lot of tuts out there. Just a question to find them out.