i need some help im my situation

i have an 89 accord and i was driving and i blew a sparkplug straight from the cylinder, i am thinking it is a broken valve, because i have been getting terrible gas mileage lately. the plug was 2 weeks old and i hadnt driven in a week and the plugs threads were completely corroded. i was wondering if my prediction was corect and if it would be better/cheaper to go gsr or try to get the stock engine fixed or buy a new car period

thanks

You said the plug was two weeks old, who replaced them ?

Do you still have any threads left in the hole ?

You said the threads were corroded ? As in from coolant, carbon, or ???

Have you done a compression test on the cyclinders ?

Which cyclinder was the plug in ?

You may be lucky enough to heli-coil the hole that blew out if it isn't to severely damaged. Believe it or not you can do this yourself.

A compression test of the cyclinders will tell you if the head needs a valve job and surfaced.

If coolant is in evidence then you may be looking at replacing the head gasket.

Things to look at.