The set-up fee is a bit much - you can find resellers that are selling / offering the gateway at a cheaper setup. Their monthly fee is a bit more expensive than some of the other gateways, but a lot of people liked it, especially when it was associated with Verisign.
Most of the gateways will give you the code to use on your secure website and offer an API to keep checkout consistent.
A merchant account itself can vary, depending on what you will be selling, how much, etc. You might also take a look at
Merchant Accounts Guidance Needed as well for a little information.