I think that it is still recommended to not tow in overdrive, but that depends on the weight that you are towing. If it is big, no overdrive, if it is small, then wee how the truck drives, if it shifts a ton and acts like it doesn't know which gear to be in, then you will want to take it out of overdrive. if it drives fine then you should be alright.
and I actually havent seen this question before
so dont worry about asking it
.
Have you checked ebay or an auto parts store for the part? I had the little button on the end of my gear selector lever fall off once as well and I found a replacement online and it fit great and stayed on without any problems
. Hope I helped