2000 Honda Civic malfunction light and transmission problem

At the same time, my malfunction light-forgive me I think thats what its called- came on, and the symbol for drive4 started blinking. The light is the one it says is an emissions system failure. I recently lost my muffler and part of the exhaust pipe, up to the catalytic convertor, so I can understand if thats why, although it never came on before. But the gear symbol is blinking, even if its in a different gear. And I think it might not have first gear at all, but im not sure. And then my speedometor stopped working also. I dont know if those are connected at all or just happened at the same time, but if you have any insight please let me know.