MS price?
 

how much is a fully assemble PNP MS kit cost and who sells them? I try to contact king, but no response.

Right now no one is assembling PNP MS kits. Atleast to the best of my knowledge no one has decided to pick up where kingofl337 has left off.
The base kit price for MSI V3.0 is $189 from diyautotune.com

I believe you can get a built MS with the Miata mods done to it for something like 400$ from diyautotune.com. You still would have to wire it into your car on your own but it is do able.

I'm in the middle of of installing my megasquirt. I have run into a few snags here and there, but it really is a pretty cool project. Plug and Play kind of takes the fun out of it in my opinion. I suggest doing it yourself. It's not really "difficult", but it is time consuming and the learning curve is kind of brutal. Much more rewarding and exciting though. For plug and play, you should go with something that is designed for that like an Xede, link, or something similar. Just my opinion

The MegaSquirt is a DIY ECU, not a 'cheap pnp' ECU.

If you are only interested in a MegaSquirt because it is cheap and you are only interested in an end product in the same manner as a Flyin' Miata Link user. Then I would strongly suggest that you get the FM Link and avoid a whole lot of grief/frustration/reading/programming/etc that you will face as a MegaSquirt owner/user.

seconded, I had issues, which the people on here kindly helped me through, but I doubt I could've solved them if the unit had been built for me.

MS is a project, not a fit and forget affair....

wait a couple months... PnP will be coming.