Is it possible to replicate the experience gained in a grad school on my own without attending one?
The short answer is: you can't replicate it.

The longer answer is: yes, you might be able to talk intelligently to someone who has a background in the field, but as previous poster mentioned, the reason why one goes to grad school is not just to learn the material, but to have access to resources. These resources are physical, but they are also mental. Part of what grad school gives you is access to people who have extensive knowledge in the field, can help direct you in your research, as well as provide crucial feedback. Without this one-on-one and group interaction, it is IMO impossible to become a researcher on par with a professional academic.