You don't need to replace them.

declare @representative varchar(255)

set @representative= 'Victaulic'

exec ('

select me.Member_Id, UPPER(me.Member_Name)as Member_Name, me.Member_City, me.Member_State, me.Member_Fax

from members me, Manufacturers m, Manufacturers_Categories mc, Categories c, Representations r

where me.Member_Id = r.Member_Id

and m.Manufacturer_Id = r.Manufacturer_Id

and m.Manufacturer_Id = mc.Manufacturer_Id

AND c.Category_Id = mc.Category_Id

and me.Member_Name = '+ @representative + '

group by me.Member_Id, me.Member_Name, me.Member_City, me.Member_State, me.Member_Fax')