Paypal integration

Hi,

I have a draft website set up.

I had the paypal process working (excluding the timeout) and then lost track of the coding, so I need a complete fresh start /full rewrite please.

I have my paypal merchant account, the auto returns etc are all active in the profile.

I have a working 'buy now' button (page X) fixed amount at £1.50, for 1 time access to an on-line pension estimator . Users cannot vary it.

What I need please is the coding (HTML/JS only) for the return page Y, to check payment was successful (and that the token has not been reused) and then re-direction to a hidden file on my website via its url Z.

I also need access to url Z restricted to only those who are redirected from page Y, so if anyone types the url direct they ought to be redirected back to page X (payment).

Lastly, once the user is successfully on url Z, I want to also limit their time on it to 3 mins. This is to prevent one person buying access and keeping it open and letting all thier mates have a free go.

So how much and how long to complete please?

Rgds