This is a common deal where neither party feels comfortable shipping first or at the same time. Both parties ship to a prearranged middle man, usually a mod or a reputable store who charges a small fee to open the box and make sure it is what was described.
3rd party trades generally do cost a little more because you have to pay for someone to at least check the merchandise out. You also have to pay for shipping twice because you have to ship to the 3rd party and then you have to pay for the 3rd party to ship to the new owner.
Make sure you discuss with the person handling the 3rd party trade exactly what they will inspect before anyone ships. Some will inspect more than others, but they may also charge more.
If you'd like to use any of these mods as a third party trader, please contact them directly through PMs or other method of contact listed in their user profile. Their services are not free but they will make sure you don't get ripped off.