So if I stake my UNI on the DAI/ETH Pool, what happens from there?
You can’t stake (provide liquidity) with UNI on the DAI/ETH pool.
You would be providing an even value of DAI and ETH.
In return, you’ll be participating in the early liquidity mining for UNI, which goes live tonight 12:00AM UTC. Check out: https://uniswap.org/blog/uni/ (Liquidity Mining section).
The amount of UNI you’ll receive from that will depend on how much liquidity you provide vs others.