lower engine noise

Hi I have been hearing a knocking noise coming from the bottom of the block on my 2003 gv with 30 000km only when the engine is warm. The dealer says its the crankshaft thats of balance. They say it will never break if I continue driving it. It is still under waranty so they desided to change the hole bottom half of the engine, block ,pistons,crankshaft. Should I let them do it or live with the knock? Thanx

If they offer, let them do it!!!