When a head gasket is bad will it damage the engine internals?

[ngrube85]

I'm looking at buying a 94 Chrysler LHS real cheap because it has a blown head gasket and is leaking coolant into the oil. needs tires and inspection, It runs great though and is in mint condition no rust or anything. My question is with the headgasket being blown would that damage any of the internals in the motor i can get a head gasket kit for 150 and change it myself,Just wondered how big of risk im taking at putting money in it if it could blow up or something be wrong inside the engine from it being bad?
What causes a head gasket to blow or leak? on a test drive it ran great picked up right away easily hit 65mph at barely even half throttle no miss or anything just slight coolant showing up in the valve covers but not in the oil. IS THIS WORTH THE INVESTMENT AND TIME OR SHOULD I FORGET IT UNLESS I PLAN TO REDO THE WHOLE MOTOR ? Also i seen a 3 step bar's leaks professional kit that is supposed to solve the headgasket problem has a few good reviews people said they used it and it worked can it be fixed with that or just better to put new gaskets and seals in it?