After 35 years in the industry I would not have any problem replacing windows and have done it several times in my life. I don't care how much free information exists on the subject, no one should try it without having someone to guide them the first time. Good measurements for the manufacture of the vinyl windows is one issue. Removing windows where the brick butts the window is another issue (saws all time). Squaring windows 'cause no one installs them with the sash closed as the instructions direct, etc., etc., etc.