Need advice on rebuilding strength?

A recent little adventure has shown me that I have allowed myself to get seriously out of shape. My vehicle was stuck in deep snow and I shoveled, drove, shoveled more for all of one afternoon and most of the next morning before I got out. It was during this process that I discovered just how out of shape I was.

I had to take frequent breaks from my efforts to not only cool off, sweating in freezing temps is dangerous, but also to simply allow my arms and shoulders to recover a bit.

The day after I finally got out and back home, the muscles in my shoulders and lower back were very sore. It has now been a couple of days and there is still a little soreness but not bad.

What I want to know is should I begin my strength building now or wait for all soreness to dissipate?

For reference, I am 54 years old, 5' 6" tall, and 130lbs. I smoke a little (about 10 cigs per day) and have a pretty high metabolism (I can eat a lot and not gain an ounce).