Get some Gojo-without pumice- from your auto parts shop and gently clean the machine head. It looks like some beautiful decals are waiting for you under the layer of gunk. Once you clean off the surface grime, you can rub a little machine oil over it and it will GLOW!
Inside the machine, put some Liquid Wrench everywhere the manual shows to put oil, and let it sit a bit. Then come back and clean that out with brushes, Q-tips, rags or whatever. Then re-oil the machine and it should run as great as it ever did.
Enjoy your beauty! These are the best machines... same model as mine in my avatar. It's my favorite to sew on and treadling is so relaxing and peaceful.