Wolfwood

okay, my case is abit screwed up. early this year, i started on this whole root canal procedure which was supposed to take 4 visits i think. i missed the last 2 and as events turned out i moved to a different country to pursue my studies. at that point of time, i just had this temporary filing in my tooth (its one of my back molars) and that's it. being the lazy procrastinating bum that i am, i didnt do anything about it till now (that's january till july). now, the filing has been totally worn out, and i have a gaping cavity in my tooth. i dont feel ANY pain at all because all the nerves were cleaned out in january. the thing is now there's this gaping cavity (half the molar) and i can see all the way to the bottom of my tooth (i think i'm seeing the base of my gums). my question is, what can be done about this? its really stressing me out because i have loads of free time now to think about it and food keeps getting stuck in the cavity. do i have to get this tooth yanked out? if so? can i replace it with anything? i really dont want to have an empty space where my tooth use to be. please advise...