Can I setup a DNS seed? I'd like to setup a Bitcoin DNS seed node for learning purposes. Would I be able to actually aid in the peer discovery process? How would my dns be discovered so that it could be queried?
The DNS seed addresses are hardcoded into Bitcoin Core (or other clients).  You would need to convince the Bitcoin Core developers to add your seed node to the hardcoded list.

You can find here a list of the requirements you'd be expected to fulfill.