When we are talking about the screen, its the screen that the weed sits on, not the carbon filter. You shouldn't ever have to change or modify the carbon filter. However if you burn it badly you will need to replace it. Just don't let the flame touch it & you'll be fine.
When I need to change the screen I usually have to pick it out with a knife.. but if you get the screen into the threaded grove then you can just turn it with your finger and it will rise up and out.
Refillable lighters are a great investment..
Vaporgenie sells the glass one as well on their site.
The vaporgenie top screws into a standard metal bowl, you can buy em at headshops that sell metal pipes & parts. So yes, the carbon filter top screws right onto the stem on my bong.