engine takes 3 times as long to start, have black smoke with starting. also slightly rough idle. could it be cause the base idle needs resetting, rather than head gasket problem? is there any other major problems that could cause it?

Check to see if your map sensor vacuum hose has become disconnected.

A disconnected or leaking/cracked hose will cause mixture (and idle) issues due to the vacuum leak. It will make the map sensor read a higher pressure (low vacuum). The ECU thinks you are under load and injects more fuel as a result. This could be your smoke (excess fuel).

Map sensor is on the firewall behind the intake manifold. Also check the connecting plug.