The Freedom is direct drive with a PWM dimming circuit, so you'll have to be aware of the Vf of each color LED in order to match them with appropriate Vbatt. For example, a blue runs the same voltage requirements as white, so it'll be fine with two 2016's considering voltage sag. Red, however, only needs somewhere around 2V, so it'll be seriously overdriven, and possibly (probably) burn up. In that case, try it with a single 2032. Dimming and modes should operate properly regardless. (EDIT: unless the circuitry requires a nominal minimum voltage... almost forgot about that.)
It's been a while since I transplanted a GS in my Freedom, and I temporarily can't find the thing in order to double check, but I believe it had to be soldered. It's an easy job though. You'll probably need some solder wick in order to open up the holes where the legs attach to the PCB.
Let us know if you have any further questions, and happy modding!