rasim
no one can garuntee that you i/c wont leak. if you choose the cm30 with a larger h/e then you will have a drop in coolant temps.
i think the question you should ask is do you want a pump that is a proven quality product or a pump that you KNOW will fail. maybe in 30,000 miles maybe in 1,000 miles but it will fail.
my friend on benzworld steve1911 has a 2002 slk32 with only 11,000 miles and his pump has already failed
any mods you perform will have inherent risk. if you want a no risk answer buy a extended warrenty from m/b leave it stock and let them worry about the issues that arise. aside from that anything can happen to any car
thats just my .02
if you go to mbworld.org the c32 section has a wonderful group of guys who can give you more info than you can handle. hooleyboy leads the crowd with his c55 and his mods are out of this world!