Critical things with BMX are the BB type and axle diameter. If your BB is still ok you'll just need to get cranks to suit the BB bearings (usually 19mm or 22mm though you can get shims to accept 19mm cranks in 22mm bearings). If you need a whole set including BB then you need to get the right type of BB for the frame though it looks like it may be a mid BB which is nice and straight forward.