Not at all!
You need to understand the problem you have at the moment before adding more confusion!
Also the car will have to be partly dismantled to fit a kill switch as it needs to be connected directly to the engine as well as wiring into the receiver,at the moment you are having problems without it so I wouldn't add it to the mix just yet.
Is this EXACTLY what you have,there have been several Baja versions over the years with different controllers so we need to be 100% sure.
http://www.hpiracing.co.uk/piw.php?partNo=113141
or is it this one,link to instruction manual
http://www.hpiracing.com/assets/documents/instruction_manuals/115891_vol04_baja_5b_2.0_rtr_060115.pdf