I've transplanted under sunlight every time I've done any transplanting with all my plants. Honestly as long as you don't leave your plants roots exposed you don't have to worry about it, just plop it in the new pot. Also, with the lighting, I recommend using CFL or T5 lights in the 6500k spectrum as they are inexpensive both to buy and to run as they don't draw as much power as a metal halide would. But once you flip to flowering id invest in a high pressure sodium light (150 watt would be good for one plant) as those really give you the dense buds that you want. You can flower under CFLs as well if you are on a budget but a HPS is def worth looking into. Remember, cool spectrum (6500k) for vegetative, and warm spectrum (2000-2600k) for flowering. Cannabis is a photoperiod plant so you will have to give it 12 hours of complete darkness when you want it to flower. Flip it over to the 12 hour cycle once you have your plant at about half the height you want it to be when its done. They usually stretch 80-100% in length in the first few weeks of flowering.
Also, one of the most important parts, PH every time you water to 6.5. This is very important otherwise you will get nutrient lockout and there will be slow if any growth at all. That was my first mistake when I started growing.