Do I need to remove the rear caliper to fix the e-brake?

Apparently it was put back the wrong way. So when you engaged the e-brake the right rear is not engaging and the cable in the console is not even, the left side is working but the right side is way off.

Do I need a special tool like a brake spring compressor?

 

with rear drum brakes, you will need a drum brake spring tool, looks like a plier but one end is curved. it is possible to do it with regular pliers, if you know what your doing, but it is a little more difficult to grab the spring correctly.

 

I have a disk brake, and do I need to remove the brake oil?

 

nah if its a disk brake then you can simply unbolt the caliper and hang it from the suspension with some speaker wire or something. this way you don't have to remove the brake fluid lines