Can this be fixed?

I'm setting up my old Trek 4900 to ride again. Im 57 and want to get back out there riding. I oiled up most of all the moving parts with TrI Flow. I also put a couple drops in my original 3x8 Shimano RapidFire shifters. When I moved the levers, it felt like it wasn't engaging anything and the derailleur didn't do any thing. Panicking, I opened them up and wiped a lot of that oil out. Unfortunately, the front derailleur only accesses 2 of the sprockets, and the back is limited, too. Its like the actuation isnt aligned in the shifter. Is this fixable? Any idea what I need to do to remedy this? Am I just going to have to cough up for a new drive train?