Is the place you are pressing on the screen (top) or on the base (keyboard area)?
It sounds like the connection between the screen and based has been damaged, or that the area you are pressing took a hard impact. The plug may have been jarred loose, it may be damaged within the hinge, or the board itself may be cracked under the case. The place where you are pressing is where the loose connection is. Are there any cracks in the plastic at this location? Taking a laptop apart is a lot of work, and I don't suggest doing it yourself.
Is it still under warrantee, or extended service plan? Dell is excellent about sending someone out within 48 hours to fix laptops, if so. If less than 3 years old, and he likes it, it will be worth fixing IMO. If it will cost more than a couple hundred to fix, then I would consider replacing it with a new one (about $600-$900 for a decent one)
If the screen goes
completely, and you need the data.... one option is to plug a regular (desktop) monitor into the back of the laptop. This will bypass the issue and give you a working picture, so you can back up the info.
You'll find the competitively priced dells just about anywhere. If you need it NOW, try Staples, Officemax/depot, WB Mason, Best Buy, Kmart, Walmart, Sams club, BJs club, Costco, Target, etc. If you want one direct and overnight, that's no problem either. Just pick one from the models that says "express ship", from the BUSINESS division. These are good to go within a day, with popular configurations. Customization is what will delay the delivery a week or so. Dell also doubles the expected delivery date, so you'll receive it in half the time it says; with few exceptions.
A friend of mine's son has one of those D520* models, which he bought through the university (required). He has been lugging that thing around for 3-4 years and it is covered in battle scars, but still works. His has Vista. He stepped on it once and broke some plastic and snapped off the metal hinge, but they came out the very next morning and replaced it. Another time he snapped off a flash drive, leaving part of it inside the computer, cracking the board inside. They replaced it free, no questions asked, within a day.
If he bought this through the school, it's likely that the warranty coverage applies until graduation. It's also likely that the school has an on-site Dell service center, and will even transfer his info over and supply a loaner unit (if necessary). Most of the time, they'll fix it the same or next day.
Anything mechanical is subject to failure or damage. My past 5 laptops have been Dells, and all are still very happily chugging along. Andy and I use two of them every day, but the older ones get un retired at industry trade shows, loaned out for a POS software booth. They're very reliable, other than needing new batteries every couple years. (easy to replace)
As far as the operating system, I suggest Windows 7. Windows XP is 2 generations behind, and has a dated look from 2001. The Microsoft Office will probably work fine on Windows 7, but keep in mind that his license may not be valid. When you purchase OEM software, you don't own the software but just the license to use it on one original PC. The license belongs to that computer's serial #, not to the owner. However, it will probably install fine anyways

If not, a great free alternative is
www.openoffice.org This is a full suite for PC or Apple that emulates the popular programs in the MS Office Suite. It can open and save in the MS Office format, etc. I don't use MS Office at all, just Openoffice. Openoffice is FREE.
I hope this is helpful
Mike