I've just reinstalled the rear brake caliper after replacing the small rear sprocket. Now I can't seem to get the air out of the rear line. On this old model do I have to bleed the front with the rear. I twisted the rear bleeder valve off and just got it drilled out and fixed. So I'm reluctant to mess with the front unless I have too.

 

You have to bleed both front and rear at the same time. Hold in the hand brake and hold down the foot brake and bleed both bleeders on the rear caliper. It will take about an entire master cylinder full of brake fluid to get it blead out.