Transmission issues

So I'm having a problem with my trans yesterday I was driving hard... and after stopping to get some gas I jumped in and first gear was popping, so I assumed I just wrecked the trans (although I didn't feel or hear anything) and took it home starting from 2nd with no issues. I get in it today to pick up a new transmission from a parts yard and the truck makes a grinding noise when in gear pops out of 1st and 3rd didn't take it up to speed to test 4th or 5th.

I'm pretty sure that the trans is screwed but is it possible that the flywheel came loose/cracked causing it to pop? It still goes just awkwardly.

Also just wanna say in the 6-7 months that I've owned the truck I abuse it almost every time I get in it but it is maintained, I change my oil every 1500k (I drive 150+ miles a day a decent amount of stop and go) with RP 5-w30 recently installed a diff fresh RP gear oil I did the power steering fluid, brake job with all fresh fluid, coolant the only thing I haven't done was change the transmission fluid I was going to do it with a clutch soon enough the truck has 110K and I'm almost certain it's the original clutch but either way it's gotta come down so I'll let Ya'll know what I find