Yep, on an aileron I would replace it BUT - this is a perfect time to practice with K2R. Get a can, last time I found it at ACE hardware.

Spray the K2R on the oily part until you have a good white coat on it. Let it dry and brush it off. Keep doing this until you have a dry piece of wood. You will be amazed at how well it works.

I have done this on 20 year old monokoted firewalls that were completely soaked. Worked very well.

One caveat though, at some point the wood will be way to oilsoaked to salvage. I pulled the firewall off my Headmaster a couple of years ago. 20 years of flying and the firewall was soaked all the way through. Weighed about twice as much as the new one I cut out. Used K2R to get the oil out of the fuse sides, put in some tri-stock and epoxied on the new firewall. Good as new!