My March 2018 Model 3 developed the AC odor about 6 months ago but I just lived with it since it became less of an issue as the weather got cooler. I've been meaning to do the cabin filter replacement and evaporator cleaning and finally had time to do it the other day. The whole thing took about an hour, including the 20-25 minutes of waiting for the foam cleanser to work.
I'm sure there are engineering reasons for why the air filter slot ended up where it is. The access to it is more difficult than it needs to be and every step of the process was more annoying than it should have been. I'm no gear head, but handy enough and tackling things like this usually don't bother me.
The side carpet panel couldn't have been designed to be removable without having to take down the panel under the glove box? I had to leave the glove box panel dangling by the wires during the process because the one attached to the LED was incredibly stubborn and would not come off (and I've done the DIY LED exchange in the rest of the cabin, so I know how easily the wire should detach).
They couldn't put the T20 screw at the bottom of the air filter cover where reaching it would be so much easier and wouldn't require a ratchet with space for only like 20 degrees of movement? Thankfully, I didn't drop the screw, but there is a pretty big hole into the center console area where it could have been easily lost.
The replacement filters wouldn't slide easily into the slot and fall into the compartment like the videos show. They required a lot of rocking and jiggling them back and forth to get them to go into place. Maybe the ones I got were warped or something.
Putting it all back together was no easy task too, especially trying to get the glove box panel aligned the right away. I still don't think I got it on right because no matter what I did, it would not go back on flush. It locked into place with the tabs and trim clips, at least.
I thought I read it was something like $140 for Tesla service to do it. The filters plus cleaner were around $50, so $90 to save my neck, back, and an hour of my time suddenly seems pretty reasonable. Plus they could done it at my work parking lot where I wouldn't have had to worry about the cleanser dripping out of the drainage system and potentially staining my driveway.
Anyway, so far the car smells a lot better, so hopefully it will last for a while.