I agree with this, however, if there is some sentimental reason for keeping it, then proceed. The early versions of this hub were the problem hubs. Later versions got better, stronger steel parts. They didn't become great. They were better. My dad had a Sears bike with Shimano 3 speed hub and used it often and I treated it roughly as a teenager, other than being sure that it had oil, and it held up fine. When I worked in a bike shop and we got a Shimano 3-speed in for repair, we replaced the internal assembly. With Sturmey Archer 3 speeds, we would replace the bad component(s) and reassemble it. The most common problem with these three speeds was the shifter. They often broke and needed to be replaced. It was an easy job and these shifter were available then.

There are three speeds listed on Craigslist and Marketplace with Sturmey Archer hubs that are probably better for putting the time and effort into. There is a Thrift Store near me with a Hercules 3-speed that is selling for $20. It needs some parts but, in the end this may be more worthy than the Kia.

If you decide to keep it, the shifters are getting more expensive on Ebay, because the supply is being used up. The bell crank seems to be going for $10 and you are going to need the cable with the adjustment barrel as well. If you want to keep it a 3-speed, it starts to get expensive. I've heard of people using a Sturmey Archer 3 speed trigger shifter with a Shimano, but I don't know how well that works. Just adjust the bell crank to line up second gear as normal.

I like the idea of using an acorn nut in place of the bell crank to lock it into second gear. At least that will get you by for now until parts or a better bike comes along.