Jessica 33914

Hi there - I bought a house with an in-ground “pool spa” - it’s about 450 gallons or so. I need to drain it, but it doesn’t have a drain valve. It has a pump, heater, blower, and filter. My question is, can I drain the pool/spa through the filter plug? The filter is a Sta-Rite with a plug at the bottom that needs to be removed with a wrench I am guessing. Single female-I am trying! I understand the steps to go through this process but I am a bit concerned because of the heater. Second question, could I replace the filter plug with a valve of some sort so that it’s easier to drain going forward? I have searched Google etc and seems like a difficult question to get an answer to. I am posting some photos as well. Thank you!!