after i press the rear brake pedal i let it go but the brake is still applied, and its applied pretty hard like the caliper doesnt want to let go.
I have to ride the bike for a little bit before the rear brake lets go.

what could this be?

Should i just go out and buy another rear brake cylinder with caliper and all, as they are pretty cheap on ebay and could be had for like 50 bucks.
or there is something simple that i can perform my self to try and fix this?

 

You should try lubricating the sliders on the rear brake caliper first before replacing. Sometimes the lube drys up and you need toadd more . The sliders allow the caliper to move back and forth when the brakes are applied and released. Remove the fourteen mm bolts (I think thats the size) you'll see the sliders inside the rubber protective boots. While you have the caliper off try appling the rear brake (not too much), to see if the caliper moves outward, then try pushing it back in with a pair of pliers. If it doesn't retract I would suspect the caliper or something further up the line (brake hose, brake applying cylinder). Then you have to get into the hydraulic system of the bike etc. Whats the mileage on the bike? When was it last in for service? Also check the adjustment on your brake pedal (may be adjusted too tight causing it to stick on). Check for any kinks in the flexible rubber line from your brake pedal to the caliper. Hope this helps.

 

new fluid and bleed the brakeline

 

and also extend and clean around the piston of any build up of gunk.

easy stuff...like a 30 minute job max...and that's taking your time!