These songs are simple.
their basically the same riff over and over and over!
here they are!
La Bamba
|-----0---2-0----------|
|---2---3-----3333-2-0-|
|-3--------------------|
|----------------------|

Thats it! simple aint it?!? 

Grease(summer lovin')
|-----------------------|
|-----0-0-2--2-0-2-0-0--|
|-0-0-------------------|
|-----------------------|

There they are!!! Rate!!