Exhaust smells like gas and blows out smoke.?

You'll need to give more specific information. A small leak might not be that big of a deal, but it can get larger, just from a temperature drop.

First off, what color is the exhaust gas? White is usually coolant, though if it's cold out, it's just condensation. Blue is oil burning. My best guess is, you've got a 90's Toyota with near, or more than 200k on the odometer. That being said, it WILL smell like gas coming from the exhaust. It's old, tired, and not as efficient as a brand new car. Don't worry about that smell. You'll want to see live scan tool data to determine if it is running rich.

If the exhaust gas is blue, you'll have an internal component failure. Worn valve guides, a bad head gasket, etc, etc. If the exhaust isn't blue, it's an external leak. Most techs will say not to worry about it. However, a good set of valve cover gaskets, or an oil pan gasket can go a long way. Find out where it's leaking from if it's an external leak. A general rule of thumb is, oil can't leak up. So if it's above the oil filter, it's not leaking from the oil filter, nor oil pan. Expect to see a little oil around the PCV hose going from the block of the engine to the intake manifold (if it has that type of system on it). Places to look are main bearing seals, pan gasket, oil filter, and valve covers.

First of all, ill give my diag of oil. Allow the oil to be warm, by running vehicle few mintues before checking, you may be loosing oil into cylinder, or burning it(assuming you dont have oil leak). It would help if you can tell us color of smoke. Sounds like your having to many HydroCarbons(raw fuel) in the exhaust. Means somewhere down the line its not getting all the way burnt. Itd be nice if your mechanic said what kinda leak. Try putting piece of paper up to your exhaust for few seconds. The exhaust has back pressure, and if the paper gets sucked against exhaust i believe that means you have too much negative back pressure however i may be wrong. As far as fuel goes, you could have leaky injector, or maybe someone moved your spark plugs wires to wrong plugs. Thatll result in fuel smell underhood, in cab of vehicle and exhaust. The list goes on and on. Try reposting with more detailed description of smell, color, temp outside, and how vehicles running