Tonight when turning the ignition key to start the Nova, the car kind of hiccoughed and didn't start. Tried turning the key again and it started but a massive amount of steam and blue smoke came out of the tail pipe. Excessive smoke or steam hadn't been seen before this moment and it hadn't overheated. Prior to this happening, my Nova ran just fine. The only smoke that is ever seen with the car is when it sits for a couple of days and then a barely noticeable cloud of blue smoke is seen, but not again during the rest of the day. Could that weird little hiccough be a pre-ignition episode that blew the head gasket? Is this a hard thing to replace? I've replaced timing belts, water pumps, clutch assemblies, so I do have some mechanical experience. I know that O'Reilly's sells a gasket kit for about $75. I've had my little Nova since it was new and I want to see how long I can keep it going. I know that it's probably not worth the labor and cost to take my Nova to a mechanic, so would I be wasting my time to do this replacement myself if it is a head gasket?

Thanks,
Maria