It is a long way from being able to sniff wireless networks out to actively inserting code in an operating system during runtime. Yes, hypothetically this can be done, but it would rely on additional security vulnerabilities to be exploitable. That said, if a MitM is possible then websites could be hacked, and the browser might be used as entry point to the OS if it is vulnerable. You would have to break through a couple of layers - but there may be shortcuts such as broken media handling or a broken driver / DMA handling.
Detecting a laptop is much easier than to actively add code to it. CPU's, GPU's and many other electronic components on the motherboard will generate a lot of radio emissions. It was perfectly possible in the old days to listen to my MSX over a bad radio receiver - which picked up much more than the frequency it was supposed to listen at - and know precisely what it was doing. I could not hear the separate CPU instructions of course, but the bootup sequence would generate very specific sounds. I presume you can do the same with a modern laptop and better equipment. Shortening or cutting off your antenna's won't "cut" the white noise coming from it. Heck, you may be leaking key strokes through the small USB cable attached to your motherboard or by sound.
If you remove the WiFi then generally you would also remove all other wireless capacities as they are commonly present in a single chip solution. In that case you would not have to worry anymore about anybody inserting code over the air. Just switching it into airplane mode or disabling the drivers will generally do the trick as well.
There is really no end to the number of security options you can go through. In the end you could TEMPEST protect your house, although that would probably gain you even more attention. Please try and balance your security needs without going overboard.
