Derive significance in difference in means between marketing target and control group

Hi all,

I am running a marketing campaign which is exclusive to 200K of my company's customers that I chose using certain selection criteria (actual customer base is several million). I set aside a 5% control group to measure effectiveness. The target group and the control group both were randomly chosen from the 200K I identified. I have been able to calculate the average revenue for the target and control group and recorded a positive difference.

My intention is to calculate the difference in means accurately.

I would like to do two things:

1. Calculate the significance between the two groups. Is the Z test the right method?
2. Calculate the confidence interval of the difference in means to 95% confidence.

Thanks PK