Your diagnostic guess, please? Car ran over rocks, emits smoke

I'm not a car person, and would be really interested in guesses from people knowledgeable about cars about what this problem might be. Thank you in advance.

The car is a Toyota Avalon 2002, not sure what engine size but probably the standard. Not too sure of mileage, has been used mostly for commuting to train station, less than 10 miles a day, since it was bought.

The accident was that at night I accidentally went off a road that suddenly went from two way to one way, and I went onto a curb that led to a wide grassy area that was also really rocky. I heard my car go over the rocks clunking. The car went all the way onto the grassy/rocky area and kept going several feet. Was going 20 or 30 mph when I hit the curb. After that I tried to start the car, and it wouldn't start. It would make a low grumbling sound when I tried to start it, but it wouldn't start. Also there was smoke coming from the front. It never had problems starting until this rocks incident.

As it was night, I just had it towed. Haven't taken it to a mechanic yet. I will, but I'm interested in your guess about what the problem is. Also, if you have guesses, any idea how much those things should cost?

Someone who didn't look a the car said it was probably an oil leak from the cover under the car getting bent and breaking something. Is that probably it?

Thanks!

No way from here to tell you what damage occurred, must be inspected on a lift, makes sense no?

Based on what you have written, my general assessment is the engine is trashed.
Have you ever had the timing belt replaced? I am assuming you have not.

What did the smoke smell like? Sweet? Like Oil burning? Something else?

Now with more information Or even pictures I could probably tell you a bit more.