The main bass riff that he repeats throughout the verses goes something like this:

e | ----------------------------------- | 
B | ----------------------------------- | 
G | ----------------------------------- | 
D | ----------------------------------- | 
A | --3/5-5---0-h3-3-1----------------- | 
E | ---------------------3-3---0-h3-3-- | 

(Riff)
I wanna marry you all over again
I wanna meet you and I wanna be friends
                                       F#5   B5
I wanna chase you all the way to Tennessee---ee
(Riff)
I?ll meet your parents at the airport bar

I?ll take you out in my rental car
                                        F#5   B5
I wanna court you on the record label?s diiiiiime

[Chorus]
 C5                       G5
Come on, baby, let?s go back to the start
 C5                          G5
Take it back, sugar, then gimme your heart
 C5                            G5                F5
Don?t you know, baby, I would do it all over again

(Riff)

I wanna buy you an old upright

I wanna accidentally stay all night
                                        F#5   B5
I wanna read the Bible and I wanna make ouuuuuut

(Riff)

I wanna marry you all over again

I wanna fall in love and say we?re just friends
                                       F#5    B5
I wanna race you all the way to Kansas Ciiiiiity

[Chorus]

(Riff)

I wanna give you a diamond ring

and then we?ll run into my ex-girlfriend
                                             F#5  B5
oh, I wanna sing songs while the sun?s going dooooown

[Chorus]