Is this a good buy?

The turbo manifold will fit no problem. The headers will need modification to bolt up but it isn't anything that your local muffler shop can't do for $50. And a catback for the Tib will not work. You must buy a catback specifically for the elantra or have one custom made, those are the only options.

Im sorry but Im still not sure about this turbo manifold??? Sorry, but can you tell me what this part is and what it can do for me specifically??
Again, sorry to be hassling with stupid questions

oh and is there anything I should buy extra fr this part in order to make it work better for me??

Do you want a turbo on your car? The first link you posted is for a turbo manifold. That is the part that attaches to the engine where the exhaust comes out and the turbo attaches to the manifold. If you don't know anything about turbos go out and buy Maximum Boost, it's a book by Corky Bell and will answer all your turbo charging questions. Please read that book before asking more turbo questions as you will need to know alot of information before you start to figure out which parts to buy to achieve your hp and trq goals. I would love to help you here but I'm not an expert myself and there is alot of self learning that you could benifit from.

oh ok, I see you have to have a turbo in order to use the manifold, ok
You helped me alot to understand. and yeah I will research it more for myself. Alrright thanks for the answers and for your time

That manifold is what collects all the gas from the engine and uses it to spin the turbo. I have that unit.