Broke my rear brake I think

New to cycling. Picked up a used Fuji Absolute 1.7. It needed rear brake pads so I picked some up and gave it a shot. While attempting to adjust the spring tension, the tip of the spring gave way from the cap, and I think a bit of the spring tip broke off. I had it all back up and working at one point, though, but the brakes were very touchy and instant. So long story short, i messed with the barrel adjuster and the cable tension screw and the spring tip is likely broken, so I am thinking I likely need a new rear brake.

Question is, what are my options if I buy a new one? I guess it can't be a V brake like the bike has on the front.
Can't post pic but it's Promax and looks like the Promax ERK, in that it's center pull. I think it's a cantilever center pull U brake, of sorts...

I'm new to the forum and I appreciate any help! And I can't wait to cruise through all the great info here...