Hello, I did some more tear out and I think I have my final plan ready. Here is a before and "after" diagram. I'd like to know if the general layout works. The vent for the shower appears to be 2" pipe and nothing but the shower is on it. The vent pipe I want to tap into for the sink appears to be 1.5" maybe 2", not sure. If you need more information, please let me know. Thanks.