head gasket on 1995 Chevrolet Astro

how do i know if i need to replace my head gasket? It smokes now bluish white smoke out of the tail pipe. Also it goes about 10-15 mph in drive mode until it hits 35 on the gauge it gets its speed after that? help me please

Asked by for the 1995 Chevrolet Astro
Head gaskets are not common failures on Astros. The engine could simply be shot.