towing hitch help

so i read everywhere where on here that if u have the towing package on ur truck from the factory u have a 6500 pound towing capacity and have the 7 pin connector on the hitch my question is i have a 2006 Tacoma double cab 2wd pre runner it has a hitch on it and looks factory but only has a 4 flat connector that's stamped Toyota and hitch has sticker that says v6 model towing capacity 5000 pounds...question is can i just buy someones ome hitch that has this 6500 capacity and plug into the factory plug i know i don't have factory oil cooler trans cooler but already bought these....i uploaded pictures of the current hitch on my truck the picture of the 4 pin connector is the other end of the 4 flat connector and connects under the bed of truck

 

I am not sure why you want to change the hitch. I assume that you already have a class 4 hitch which is rated at 12,000 pounds and even a class 3 is rated up to 6000 pounds depending. If you need the brake controller ability just add some extra wires to what you have, but keep in mind your truck is not rated for the heavier weight regardless of hitch(above 5000 lbs.). Here is 3 links that might help.
http://www.etrailer.com/faq-hitchclasses.aspx

http://www.youtube.com/watch?v=qUz9dMyASUw

http://news.pickuptrucks.com/2013/03/towing-5-things-to-never-overlook.html

 

You can't (or shouldn't) just swap out hitches and suddenly assume you have a 6500lb tow rating.

Not only does the towing package get you a transmission oil cooler, but also engine oil cooler, bigger battery, bigger alternator, etc.