Problem with rain coming in windows
 

Whenever it rains water runs into the front driver and passenger door. Where can I buy the weather stripping and which strips should I replace?

Before replacing the weatherstripping try applying some silicon grease to the existing rubber WS on the doors and see if that revitalizes it. If not the WS can be purchased from a dealer, certain auto supply stores, and from various online auto parts sites.

Any idea on the cost of replacing all the stripping around the door?

Nope.

Is the weather stripping worn out and/or missing chucks? Or does it look "okay" but still leaks?

If it looks ok, you might want to take a look at your door hinge pins.

It looks kinda worn out. I'll try and take pics and post. What could be wrong with the door hinge pins?

Through use (abuse - letting them swing open without restraint, etc) they can get 'egged-out', take an oval profile and have to be sleeved or replaced.

First check your door hinges as stated. Try lifting up on the back of the door with it open watching the hinge area for play. If you find play, then the hinge pins and bushings need to be replaced.

my door leaks as well
 

you might want to check the actual welds that hold the door hinge on, mine is completey cracked on the inner side and thats why mine leaks, im assuming i got a friday blaser from the gm plant,,,haha, it strated with the driver side and a year later the passanger side cracked. hope this helps

This is my suggestion. Mine leaked horribly until I replaced the pins and bushings. New weatherstripping from the dealership was super expensive, whereas two sets of pins and bushings from the local parts store and a little bit of my time was less then $10.