Problems with overheating on 2002 Oldsmobile Silhouette

Just had intake manifolds replaced due to antifreeze leak; now Im being told exhaust is leaking into the coolant system causing the vehicle to overheat. What needs done now to repair; any ideal of cost. Any help would be greatly appreciated.

Asked by for the 2002 Oldsmobile Silhouette
could be cracked head or headgasket 3.4 engine or replace engine be cause sometime you can not find a crack in a head or a bad headgasket best to repace heads with new ones