There is no need to take your Toro lawnmower into the shop to have the drive belt replaced. Replacing the drive belt is a fairly simple task and can be completed in about 45 minutes. Be sure that you have the correct drive belt size for your mower. You can check online for the correct belt for the model number of your mower or have your lawn shop look up the correct belt.
Carefully clean out any debris from the mower, taking care to avoid the blades or other sharp parts. Wear protective gloves if necessary. Ensure that the mower cannot be turned on while you are servicing it. Keep your mower's instruction manual handy. If you no longer have it, note that many manuals and parts catalogs can be downloaded free from Toro's Web site (www.toro.com).
Remove the lawnmower deck. This procedure varies from model to model. You will need to remove the screws that hold it in place. Remove the spark plug and the blade. Refer to your owner's manual for specific diagrams for your lawnmower model.
Remove the belt guard around the engine pulley on the crank shaft. Remove the belt from the transmission pulley and from the engine shaft. With some models you may need to unbolt and lower the transmission and axle assembly in order to remove the belt from the transmission and engine pulley.
Put a new drive belt on the transmission and the engine shaft. Reattach the blade and spark plug and put the lawnmower deck back on. You should not have to stretch the belt excessively to install it. Improperly installed belts can slip or get torn up and ejected if caught in the machinery.