You might want to look at:

https://unsloth.ai/docs/get-started/fine-tuning-llms-guide

I've heard of people using anythingllm for this purpose.

Basic rag is almost stupid in how easy it is, though. You grep for keywords, take the surrounding paragraph, then stuff it all into your llm prompt.

The next upgrade is to automate keyword extraction by putting your documents into a vector store and search by vector similarity.