Like Cari mentions; the stop motion washer has two points protruding outwards, that's the correct way when assembling. The triangular placed points on its' outer circumferance can go on two different ways, and it's mostly a trial and error of getting them right.
Here's a blog post on the subject.
Fixing up a 66 is well within doable for a beginner, it's always a lot of work when you have to go for a full refinish of the shellac. I hope you found nice decals. A new bobbin cover and needle plate (aka throat plate) can easily be found on the web, both brand new and good used condition. The needle and presser bar shines up like new with the right stuff. I found something called Quick-Glo and it did a very good job on the steel and chromed bits on my 201. Generally I find paste polishes for chrome and steel does a better job than liquid polishes. There's loads of brands and some are better than others.
Detect all oil pionts and add a bit of oil every day for a while, let it seep in, wiggle the handwheel now and then and it will eventually free up. Keep on oiling and test sewing, it takes a bit of time and effort to dissolve and flush out grime and rust. If you have stripped and repainted the body already, the rest will come a long much easier. It's a nice model, if you aren't familar with machines like this, I'm sure it will surprise you in a good way. They are very smooth, capable and well behaved. I have added a few accessories to my 201, particularly I like the buttonholer and a walking foot.