Changin' Cables

[Chuckles1981]

I could'nt change gears on my new MTB which is only about 3 months old, i was missing the first 3 gears.

I toke it into the shop and was told that the cable end has come loose in the housing end and the end was all frayed the guy said he's only seen this once and out of a million cables only 3 fails like this and ever since i have all my gears.

But my question is if it happens again how would i go about changing it myself.. i know there are diffesnt cables for brakes and derailers, I just want to know how much they go for and whats some ways of changing cables cos i know they will loose they tension also.

Thanks Guys

[LuckyPierre]

... I toke it into the shop ...

Well, there's your problem

... if it happens again how would i go about changing it myself...

Cables cost about $2 each (or more for poncy ones).
Instructions are on the Shimano website. This link takes you to an example - just navigate to the pages from the 'Technical Documents' section on the appropriate product pages.
I'm sure that there are plenty of other sources too.