I'm a 1.37:1 guy myself, up to 1.85:1 is tolerable but wider than that and I generally hate it with a passion. Most people can't frame for jack at those aspect ratios.
I would add that make sure you get a K-3 with the M42 screw mount. Some out there have some kind of bayonet mount which will leave you stuck with the zoom it comes with.
The proof should be in what type of reel the film comes back in. Dwaynes puts the film on a white or grey reel inside a white cardboard box. Switzerland was always a black reel with black snap on cover. I stopped getting the black reels in 2002.
I've had no problem with slow films like K40 where I just load in the shade or just put a jacket over my head to create heavy shade. Higher speed film like 250 would have me a little nervous so I personally would use a changing bag.