Questionable contractor but already signed contract

[Christian Bors]

So my contractor, lets call him John, that I usually use is jammed packed until mid to late December.  On one of my properties, the carport roof needs to be replaced.  When I went to look at the roof there happen to be a contractor, lets call him Steve, working on a roof down the street.  I asked him to take look.  Steve's estimate seemed reasonable and he said he could complete the project in 1 day next week. So I signed the contract that states 850 deposit and 1500 upon completion.  I am suppose to give him a deposit on Monday.  Stupid mistake.  I have no idea if he's good or bad contractor.  No referrals.  I know nothing about this guy.

After speaking with John, my main contractor, a couple of red flags popped up.  The first was the Steve wanted to lay the new roof on top of the old rotten wood.  He said this would save cost.  Steve also  told me the roof was 3.5 square.  I asked John to take a quick look and see if what Steve is saying is legit.  John told me I should absolutley rip off the rotten wood.  The weight could cause problems down the road.  Also, John told he measured the roof at 2.6 square and I shouldn't be billed for more the 3 square.  

I called Steve and mentioned my concerns.  He said he couldn't remember the exact square of the property.  He did a lot of estimates that day and didn't have his notepad with him when we talked.  Steve also said he could rip off the old roof but it would cost another 400.  The total being 2750.  John quoted me a price of 2500.  Usually John is not the cheapest contractor, however I know he does good work so I don't mind paying more.  I trust him.  But in this case, John is cheaper!  Its a no brainer. I should wait until mid dec (its not an emergency) and have John replace the roof.  My concern is I already signed a contract.  I have not given him any money, but would I be subject to ligation?  What should I tell steve, and how should I handle this situation?

Also, another concern of steve is he looks like he just got out of prison.  He has tattoo's from head to toe.  I don't mind tattoo's but it does not look professional.  

Thanks for the help,

Christian