Bit for Round Over on Trim for Window
I am new here and new to routers. I just bought my first router, a Porter Cable 7538 on ebay for $102.50. It is missing a base plate. I want to use it to round over the trim boards on a replacement window I am installing. I was thinking of a 3/4" round over with a 1/2" shank. The boards are about 1". I don't think they are a true full 1 inch. Should I be looking for a smaller round over than 3/4"? Also do you think it would be better to router the boards before or after they are put into place. I will have easy acces once they are nailed.
Also should I just get the Porter Cable base plate?