Hi Kyle,
When using 120 film, pull the knob marked 'R' out and rotate it 90 degrees to keep the pin from casting a shadow on the image area. You could use tape or even glue it to fix it in place if you never use the 35mm kit.
The 635 is a nicely-made camera and it's not 'crudely made' but it is fairly basic compared to the Yashica-Mat line. As Randy said, the Yashikor 3-element lens (unless you're lucky and have a late model with a Yashinon) isn't crash-hot but is adequate if you stop down, and can make a good, sharp neg. The bokeh is oddly circular. The centre is quite sharp but that falls away toward the edges, in 35mm mode it's a nice, sharp portrait lens.
Using the camera in 35mm mode is an interesting experience; it's easy to use in portrait orientation but a bit more awkward for horizontal images. You can use the sports finder but you'll have more parallax. Using the ground glass is more accurate on framing but getting used to the upside-down viewfinder is a bit... unnerving! Not a great camera for action shots!
It's possible to get 60mm-long, full-width images on 35mm film; fit the cassette adapter to the feed spool and the take-up spool but leave out the frame and backplate. Your images will cover the sprocket holes. The downside is the frame counter won't be accurate, you'll need to work out the actual amount of turns per frame and there's a possibility the film won't lie flat across the film plane. My solution is to glue cardboard across the camera back. There's a very useful website at
http://www.yashicatlr.com/66ModelsPage6.html#yashica635.
Have fun,
kevs