When in SOlidworks (no part or drawing loaded) search to open the Drawing and before clicking open click references below
Then it will show you which part it references. This might be the part name before you changed it. To change it to the new part click on the part name in the references box and you should then be able to pick the new part reference
This should then work.
Thanks a lot you guys all had great answers. I appreciate the help!
depending on the version you are running you have a couple of options.
1. use the "references" button on the file open dialog (2015 SOLIDWORKS Help - Open Dialog Box )
2. use the replace model command (new in 2014 or 2015 - I forget) (2015 SOLIDWORKS Help - Replacing Model in a Drawing View )
File > Open
Highlight the drawing file but do not open
Select References (a tab along the bottom of the screen)
Double-click the file under the Name column
Browse to and double-click the replacement file
Open the drawing file & save