You may want to take advantage of your 'down time' to do some research on "bicycle fit" or "bicycle riding comfort". If you are used to a more upright riding position, it may take a while to get used to the forward riding pos. of a road bike. Your age, flexibility, and core strength will also factor into riding comfort.
Basically, your saddle height should be set so your legs are just a little less than fully extended when you pedal backward with your heels on the pedals, and front-to-back adjustment is set so a plumb line dropped off the front of your knee (pedals level, front knee being checked) just touches the front of the pedal spindle. Saddle should be level. Reach to the bars is adjusted by changing stem length. With threadless stems, bar height and reach can be changed by using a different length and/or angle stem.
Saddle can be the cause of 'sorebutt', but is not usually to blame for lower back pain or hand numbing. Lower back issues can be a result of riding position or lack of muscle tone. Hand numbing is usually an indication of too much weight on the hands. Riding position, and maybe bar height would be my guess.