Hey Roger, thanks for giving us a shot.

If you're going to bypass the checkout form at /cart/checkout, you're going to need to do 3 basic things to get to the Review page:

1) Validate the customer's input yourself.
2) Create a new order with the customer and product info in the in_checkout order state and set $_SESSION['cart_order'] to the order ID.
3) Set $_SESSION['do_review'] = TRUE and redirect to /cart/checkout/review.

In your own module, these things can happen in your form's validate handler (#1) and submit handler (#2-3). Simply return the URL from your form's submit function and it should take care of the redirect for you.

You'll need to account for payment with this setup somehow. At the moment, there are a couple payment systems (PayPal WPS, 2Checkout.com) integrated that work by redirecting from the review page to the gateway's payment page... if you're not using either of those, be aware that payment info is normally collected through the checkout form.