The body mounts are the mounting points that attach your Jeep body to the frame.
Your Jeep should have 11 mounts total.
1 in the front center just under the radiator.
3 down each side between the front wheels and rear wheels. (1 just behind the front wheel, 1 about center of the door and 1 just infront of the rear wheel) The ones that he showed you are the ones under the door. If you locate them again and look to the right and left along the frame you will see the other 2.
2 others, 1 on each side on the inside of the frame rail at the top of the rear frame arch just in front of the gas tank
The last 2 are on the rear corners 1 on each rear corner.
As I said earlier this will give you a total of 11.
They will be a big pain in the butt to get out if they are badly rusted. I ended up breaking 6 of the 11 bolts trying to replace them. depending on what bolt gets broken it will probably require you to cut into the body tub to remove the broken end of the bolt and replace the plate with a new nut.
Here is the kit that will work well: http://daystarweb.com/productdetail.php?productID=313
I am not sure how much that kit will cost you I wouldn't expect it to be more than $80. I purchased a kit from Daystar but I got one of their SuperKits that replaced all the bushings on the body mounts and all the suspension parts... That kit cost me around $180.