PCInk - 11:58 am on Jul 28, 2011 (gmt 0)
Instead of replace, you should find that INSTR should give you the position of the first word. Then you can use something along the lines of:
LEFT(col1,INSTR(col1)-1) + 'bigwidget' + MID(col1,INSTR(col1)+LENGTH(col1))
Probably not the most efficient way but it should work. It is psuedocode so you might need to lookup what should be used for LEFT, MID and LENGTH in the language you are using.