Well the numbers and letters are just the notes, like the letters are the strings, E is the lowest string on the top of the neck and G is the highest string on the bottom of the neck, and the numbers are the frets, like 1st fret 2nd fret ect. If you ever look at a guitar and see near the end of the neck the slim fret with the two dots on top of each other, where the frets become thinner afterwards, thats the 12th fret, its a good marker to help you find your place on a guitar/bass guitar : p
So like, with that its just those three first chords I posted then after that you repeat them and play the alternate part. As for rhythm/timing, you cant read it with this : p It merely shows you how to play the chords, haha. I recorded it for him so he could get the feel for it himself.
IF you are interested in hearing it, this is what it sounds like here-
http://vocaroo.com/i/s0b3MyJR3ggS
Its an idea I have for a song but I cant come up with a good alternate melody to go along with it so I asked another bassist to help, and he showed me how to write that out so he could find the chords easier : p
And you should totally learn to play! I didnt start until I was a week away from turning 21, haha. So you arent too old to learn : p
Id recommend bass guitar, as I think its more versatile. You can both come up with melodies through chord work just like a guitar, and you can make your own rhymthic bass lines to accompany them with your bass : p And after learning chords on a bass theyll be way easier to learn on guitar : p It can be discouraging because the strings are larger and farther apart, and like even after years of playing it still makes my hand cramp after a while of playing but its way worth it : p
But if you want to play with the twinkely sound of a guitar, then you should totally go for that : p The strings are thinner and closer together, so where a bass has more meaning in one note, meaning you can just focus on one note at a time if youd like, a guitar generally puts more focus on playing each string together due to them all being together. It has its own difficulties to master like any other instrument : p
Sorry for the long response, its just a topic I have alot to say about : p