are you doing the tile as well? As an installer I wouldn't trust someone else to do the waterproofing. And then it should be no more than a days worth of work plus your cost of materials which would probably be around $600-800 assuming a tiled pan and depending on niche, drain grate, curb, etc options More on reddit.com

You’re better off buying kerdi board. The membrane needs to be bonded and then troweled to get excess thin set out. If you ever wall papered, it’s 5x worse than that. With the board you just screw in with washer backing and seal over the screws with small pieces of membrane. You can also just used cement or hardi backer board. That said, you can cut kerdi with wall board knife. It’s lined so I lay it on plywood and just cut free hand. Very easy. I’ve used the shower pan to avoid fabricating a pan. Sure if you’re a pro it’s a days work, but for DIY the pan is just cut and go. They tell you wall first then pan, but I reverse it. I want the walls to overhang the pan and I double seal the joints. First with caulking then with membrane. You just need to cover pan membrane while working on walls as you can scuf the membrane up. Just use a painters drop cloth. Once everything is up, I tile the pan and the cover it with scrap wallboard or something. Then tile the walls. I wait to grout everything till the end as loose thinset will find it’s way to shower pan tile. OBTW, you need the roll of 5” membrane to seal all joints…wall to pan, wall to wall and screws. It’s expensive so measure what you need I just finished a small shower (54x45) and used a whole roll. About 8” left at end. More on reddit.com

I'm curious if you blocked the subfloor from underneath - 2x6 or 2x4 around the perimetre of the cutout for the old drain, to support the subfloor and rid the deflection. More on reddit.com

I have and followed this guys videos https://youtu.be/Au0XLFEmqrk He has 3 or so videos. I think you want the pan, then the cement board/drywall. The wall boards will fit over the lip of the pan so any water penetration makes it to the pan, not behind it. More on reddit.com