Do not know repair out of service valve? Actually, about and is this article.
First sense search specialist by repair valve. This can be done using bing, portal free classified ads or corresponding community. If price fix you want - can think question exhausted. If no - then have repair their hands.
If you still decided own perform fix, then first must learn how repair valve. For this purpose one may use rambler or yahoo, or read theme forum.
Hope this article helped you solve question. In the next article I will write how repair interior doors or interior doors.