Oil leak on Spark plugs

My ‘00 Celica had an oil leak when I got it, but I didn’t know exactly where it was, nor did I have the time to look. The other day I was installing new Spark plugs, and found out that there is oil in all “tubes”, and a lot in the first one. Is there a way I can fix this that’s not insanely expensive, or should I just get a new engine?