I am very much a DIY'er and doing my own HVAC repairs have never been out of the question. Actually, I have rebuilt a couple of systems, less the pressurized parts of the system....
If you live in the US you cannot legally purchase most domestic refrigerant without EPA Section 608 certification. Most supply houses will ask to see your cert card if they don't recognize you.
If the concept of a reversing valve is wholly alien to you, I cannot recommend you DIY your issue. Just hire someone, it goes beyond convenience or annoying risks, it's your safety that I'm questioning. Frostbite, electrical shock, poisoning, risk of explosion, severe burns, suffocation, there are so many ways that trained techs get hurt or killed when they don't respect the safety element. No way in hell am I going to tell a stranger on the internet to take that risk for themself or someone around them.
Please just hire someone.
Edit: just realized you're not the OP. Still gonna leave this up. This kind of work is simply not suited to being done by non-professionals.
Checking and charging HVAC: Plausible DIY?
I am very much a DIY'er and doing my own HVAC repairs have never been out of the question. Actually, I have rebuilt a couple of systems, less the pressurized parts of the system....