Water Impeller for 2007 50TLR & 2006 40TLR

I'm looking to replace the impeller (water pump) on 2 motors. Wondering if they were both the same. Any suggestions on the part number(s) & where to find it inexpensively ?

[boats.net]

Yes they both use same impeller 6H3-44352-00-00
http://www.boats.net/parts/search.ht...CASING+DRIVE+1

Thanks very much. Is this difficult to change & are there any other parts required to replace it ?