Budget $2000. I'm serious about this. The things you buy will last you for years, and $2000 will pay for itself if it saves you two weeks of sick time or a couple of doctor visits.
You may not actually have to spend all of that, but you are going to want:
* An excellent chair ($800 range. Feel free to try the cheaper chairs... I have an Aeron but frankly have no idea if it's worth it. I bought it after using one at work for six months, and discovering it was okay. Testing chairs is difficult and expensive, so I recommend starting out in the midrange rather than spending months working your way up from the $50 OfficeMax chairs. If you find that the more expensive ones are 5% better for you, spend the money.)
The goal with chairs is adjustability. I recommend a chair with adjustable arms, because sometimes when my shoulders get sore I move them up to brace my elbows during rest periods.
* An excellent keyboard. MSFT natural keyboard is a great value, but I switched to the Kinesis Advantage Pro six months ago, and it kicks butt: http://www.kinesis-ergo.com/ ). It costs something like $350. It looks like it was designed by aliens. You will feel like an idiot for the first week as you relearn all your typing and gradually remap all the keys to your favorite locations. If you don't know how to touch type... you will learn. But then you will experience the joy of feeling like you are typing while barely moving your hands.
* I concur with the Ergotron monitor arms. Being able to adjust the monitor to exactly the right position is important.
* A proper keyboard drawer. You want the kind with the arm that lets you adjust the keyboard to arbitrary angles and heights, and slide it in and out. If you use the mouse, you want to be able to mount the mouse at one side. Something like the ones on this page: http://www.ergoindemand.com/keyboard-tray-adjustable-shelf.h... . I would tell you the brand I use, but I picked mine out of the trash by the side of the road. (Arlington, MA -- there are real advantages of living in a startup hub!)
Then you have to hack. Once you've spent money on the raw materials, ergonomics is a game of inches. I have one of those damned expensive Aeron chairs, but just this year I discovered that it doesn't provide enough upper back support, so I strapped a cushion to the top with a bungie cord :). Cost: maybe $20, and the pain is gone. My right arm got sore using the mouse. I discovered that if I took my mouse support off the keyboard drawer and reattached it using a different bolt and some homemade washers, I could raise it by four inches. And, just like that, the pain went away.
See a physical therapist. If you do nothing else, do this. The good ones are amazingly smart. Don't wear wacky gloves or wrist braces without consulting one. It turns out that most of my own occasional wrist pain is caused by nerve pinches in my neck, and treating the wrists is mostly a waste of time...
Oh, and of course: don't type on a laptop keyboard for more than an hour or two every week. Laptops are ergonomically terrifying. Sorry to have to break this one to you. :)