You can get 3rd party Sims/microSims that could potentially work. If you want to use it as an Itouch you can probably get any old sim that will fit and put it in. With Sprint though usually it says you're connected to Sprints network even without a SIM, atleast it did with my 4s that was locked to Sprint. But I couldn't for the life of me unlock it from Sprint. Supposedly there was a way awhile back for jailbroken Iphones but it got patched. I'm not 100% sure about Iphone 5. I suggest googling if no one hear can help.
When my friend lost his little spring during a LCD/Digitizer repair it had no color/backlight on his screen so I'm assuming it grounds the digitizer. I'm not really sure if you can find a replacement for it. I've heard of some people having no problems without it, some say any replacements screens they have refuse to work without it.