I get an alignment anytime I mess around with suspension parts, but I'm over cautious like that, beats buying new tires. I haven't done my rear, only the front.
The YouTube video shows a conversion, but the only difference is you will have to expand the the control arm more to get the old coil out, he didn't have to do it until he put the new coil in.
I'd also replace the pads at the top and bottom of your coils, depending on your road conditions and mileage