Take a look at the methods used in these two demo files:
One method found in both files uses a text field with an auto-complete enabled value list such that typing data into the field "prunes" the list of matching names to fewer and fewer matches. Another method found in the "enhanced" file demos "search" portals that use one or another partial text matching strategy to control what values appear in a portal, which can then be clicked to select the value.
Both methods rely on scripting to enter the selected ID number into the correct field to link records relationally by ID. The scripts also can handle issues such duplicate names.
FileMaker 12 users: https://dl.dropbox.com/u/78737945/SimpleNameLookupDemo.fmp12
Pre FileMaker 12 Users: https://dl.dropbox.com/u/78737945/SimpleNameLookupDemo.fp7
I used the first file and set up my search function just like the portal on the top of the page. It worked perfectly! Thanks!!