It sounds like it might be a situation where both parties are new and have no standing in the community or feedback rating to rely on to instill confidence in the transaction. As you engage in the community and kind of get a feel for the etiquette and social norms around here, I'm sure you'll be fine. I've probably transacted between 75-100 times on PCF and have never had a problem. If someone was new or lacked a feedback rating, I would simply ask them to complete their end of the deal before paying or shipping.
When he suggested a 3rd party escrow, he may not have anyone specific in mind. In this set of circumstances, I'd suggest finding a mutually acceptable reputable member to receive the funds. There are literally at least 100 people here who would probably be willing and trustworthy. Once acknowledged, the seller could ship and when you receive the chips, you could direct the 3rd party to release the funds.
You could also do it where the 3rd party receives the package, but in that case the chips would need to be shipped twice - which creates more work for the 3rd party and more moving parts in the transaction to where something could go wrong.