It sounds like you really should talk to an electricion. In advance, I would check the circuits to the lights, doors and saw. Are they all on one or are they separate. You can do this just by shuting the breaker and checking what is working and what is not. If you are using the garage as a dedicated woekshop then you really should look into placing a submain in the garage, maybe for a 60 amp service then you would have enough power as you grow. In my shop I have a 100 amp submain and have no problem with any dimming.
In addition, if your saw is capable of 240v then by all means convert it is better and you will be spreading the power draw and be more efficent. Its is also better for the motor may even reduce heat.
Working with electricity is not a big problem, but if you are not farmiliar with codes and basic wiring you could be in trouble. Yes, it can be expensive to hire an electricion, but you can't put a price on safety and piece of mind.