I was just wondering how important are major 7ths,9ths and so on?

thats a cilly question... they add colour to your music

I was just wondering because i have problems stretching my fingers to reach the notes.So i figuered if they are not important why bother.

brings it to life

If they're in a peice you're trying to play, then they're important. Otherwise, I don't know why you would bother trying to play them.

I figuered has much but how often do they show up in music?

Dominant 7ths show up in a LOT of songs. Major 7ths and 9ths aren't as common, but they're necessary to create a particular atmosphere. If you have trouble reaching them, try rolling the chord. (You should be able to reach 7ths, though...I'd say most people ages 10+ can reach a 7th.)

Again, this is one of the dangers of learning on your own: you tend to dismiss stuff you don't think you'll need.

Refresh my memory whats a dominant 7th.

Dominant 7th = major triad + minor 7th
Major 7th = major triad + major 7th

Lol, that slike saying if you had no bones in your body.