All you need to know is that the matched text is going to be available in the replace textbox using the '$' dollar sign.
So to access the first matched element use $1, for the second $2 and so on.
I had an old method with hundreds of lines doing calling a getAttribute("X") and casting the result to a string.
(String)object1.getAttribute("X") (String)object2.getAttribute("Y") (String)objectN.getAttribute("Z")
I had to change them all to use a new method that checks if the attribute is null. So the new line would be
getSafeStringAttribute(object1,"X") getSafeStringAttribute(object2,"Y") getSafeStringAttribute(objectN,"Z")
With this simple regEx you can do a replace all!
find : \(String\)(.+)\.getAttribute\("(.+)"\)
The first (.+) will match the objectX part while the second will match the attribute name.