So, I finally tore into the old gearbox. I'm definitely not more than an r&r home mechanic, but I see no visual damage (ground gears, broken parts, or metal chunks). Now I'm confused as to what may have gone wrong. Before I put the new one in it would grind horribly in high or low but would move under minimal throttle, better when the oil was thick and cold. This was after a pretty good impact and being really stuck. Anyhow, if anybody needs parts, or has an idea of what I should look for, let me know. I've already got the new one in, so........