I sympathize having had a motherboard on my desktop go out a few weeks ago - same symptoms, a blinking power light and nothing else.  In my case, I can see that a capacitor on the board is leaking so I'm pretty sure it's dead.  Your nephew may be able to help but as Pakled says, there really is a difference between swapping parts in a desktop, which pretty much anyone who can use a screwdriver can do, and laptops.

Unless you absolutely need a laptop, I'd think you could upgrade or replace your desktop for less than the price of repair and have a better system.  Hopefully Dell will cut you a break and at least give you a substantial discount on a new or refurb system - assuming you still want one of their products.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken