Yes you can sell common stock and it is rather easy. First you need to find out if the stock is in certificate form or held in a brokerage account. In other words, find out where the stock is located and in what form it is held for you.
From what you are telling me it sounds like the stock is held in probate. If this is the case, you have plenty of time to find out in what form the stock is held. If it is held by the lawyer handling probate he can give you this information. Once it clears probate you can have the stock transfered to your own brokerage account or your bank can most likely handle the transfer. Once you have the stock it is just a matter of telling your broker or bank when to sell. If your bank does not handle stocks, then open a Scottrade account, have the stock moved to your account and sell it by placing a call to Scottrade to sell it or sell it yourself online.