Yes a good GMAt score will definitely help. Besides scores, GPA, your SOPs, LORs, Resume and work experience also make a difference. I think you should concentrate on your positives and try for a good GMAT score. Refer to manya education site for details.
I've posted before.
I am too young for an MBA.
I should wait for a year or two
Now I am planning to apply for a business-related MS MSC or MA
In the US or in UK
My GPA is low
Would a high GMAT help me compensate it?
I dont think these schools require a GMAT.