I'd recommend huggingface's transformers library. You probably don't wanna be finetuning these LLMs yourself since that's a big endeavour, but secondly because they already have the NLU capabilities to solve your problem. You basically want to train a single classification layer on top of your models output. I believe it'll be something like "CausalLMForClassification" in the huggingface docs.

As far as resources go for finetuning I haven't found many great resources. But again, you probably don't wanna be finetuning these massive LLMs for your particular use case -\_/- Buenos suertes.