Hello to all!

I am a new user of K2, i just installed it in my site.I think that K2 fits my requirements, but i have some questions.

I want the users of my site, once registered, to be able to enter content in the site on their own.

I want to put a search engine that will search with creteria. For example, i want to search for a car, i wiil choose the field of the brand, the field of type, the field of model etc.

Also, i want visitors to put a request form for users. For example, one user wants to buy a Toyota car in the price of 10000 Euros.He will fill in the request form and will click the Send button.After,this request will be sent via email to the Toyota traders which are already members of my site....

How can it be?Is there any extension for this jobs?