This is an older watch of my wife's and would rather change the battery myself.

What battery size/model does this use and what brand do you suggest?

Thanks in advance.

 

This may be helpful to you:
http://www.horologycrazy.com/2011/06/omega-constellation-ladies-battery.html

 

Do you have the proper tools and is the price you’re saving worth the risk of causing a gouge in the case back— which cannot be remedied?

 

By the time you buy one battery and the tool you a few $ behind