OT: seeking group wisdom on selling stuff online

[6keb1 at qlink.queensu.ca (Kareem)]

I'm selling some car parts on vortex. I'm a newbie at selling and this guy is new to vortex and doesn't have many posts. The guy also asks for overnight shipping to him (he's in US, I'm in Canada). It's mondo expensive to do that, but he accepts the quote. I am surprised because it's almost not worth it. Now says he can only pay via international postal money order and wants me to ship immediately after I receive it since he needs part by Friday. Question: can't this money order be cancelled after he sends it. I bet my bank won't cash it immediately. This sounds fishy to me but guy really wants the part this week. I don't want to be ripped off of course. My question: Is this a common scam or are the US international money orders safe?  We're talking about a US$100 transaction here. Thanks folks,
Kareem
81 S
88 2L 16v