I am going to replace the bushing on my rear boxed control arms for the 71. Anything I need to know before I start? Do the new bushings need to be pressed in? I don't have a press but I have access to one. Do I just drive the old ones out? Do one are at a time? etc.

I just did that this week...
The old bushings were easily removed by drilling about 6 holes thru the rubber, knocking out the remaining rubber and inner sleeve. Then I used an air chisel to collapse the outer shell, which then fell out.
New bushings were frozen and installed with a small press, taking care not to distort the ends of the arms.

You can use an old socket to place inside the arm so it doesn't collapse, twist, or bend. That's what I did and it worked out pretty well on my 69.

put some heat to the rubber itself.. but watch out, that sucker willl practically fly right out.. an air chisel works well for pushing out the old sleeves..

I took a $3 exhaust "adapter" than was the correct (a bit larger) OD that the bushing and sawed in 1/2 lengthwise, then cut the two halves to length to just push fit inside the "ears" on the control arms, around the bushing hole. Worked great to stop the "ears" on the control arms from collapsing.

Just use a screwdriver to pry them out after the bushing install.