Doing it yourself or not depends on what you are willing to pay. IIRC, my dealer wanted about $600 labor to do it, and that was over 10 years ago so it's probably more now.
You probably don't need a whole dash if it's only the top cracking. That part is called the upper dash pad, and it is a separate piece from the rest of the dash. The problem with replacing it is the whole dash has to rotate out onto your front seats, but the dash rests on two pins at the bottom on the ends so you don't have to take it out completely.
Doing it by yourself can be a handful. It would be better with two because the dash is heavy, and you can work on both sides at once. The Haynes manual has all the instructions, but you'll be flipping back and forth from section to section because of all that's involved, e.g. disabling air bags, dropping steering column, disconnecting the gear indicator, etc. If I had it to do over again, I would make copies of all the sections I needed. Set aside a whole day to do it. It's actually not difficult, just time consuming and you'll need some strength to rotate it back into place and hold it there while you bolt it back in.