I would go with Trex, Timber Tech or Azek would be the brands I would go with. Both offer decking and railing. As for the rest of your porch, I would say it would be about 1500-2000 for the deck it self with out the decking. You would need to knock out your front stoop, add a ledger board and the rest of the framing plus footings for the front portions. I would probably add 1.5-2x that for the columns and over hang due to having to cut into your siding and attach it to your house. To be safe I would guess it would be around $5-7000. That is a broad guess, but with out knowing exactly what you have going on there. There are so many builders out there begging for work that you should get 3-5 bids, and never take the lowest price. One thing I would check though is with the city in regards to how close to the property line(sidewalk) you can be. You are set back a ways, but you never know with city ordiences.