Thanks guys. I was pretty sure I could use any Shimano 7 speed shifter.

Just one more question.
If I remove the existing cable from the outer cable to install a new shifter which usually comes with a cable I'm worried about fishing a new cable in since most of the outer cable is in the frame.
Is this something I should worry about?
Can I remove the cable from the shifter end of the old shifter and replace the cable on the new shifter without removing the cable from the outer cable?