I've used paypal for over 10 yrs and only got screwed one time. i usually pay with a credit card and have some recourse if something goes wrong.
Postal MO's are safe if you cash them at the post office before you ship the parts, however there are lots of phoney postal MO's out there. The very safest way is to setup a 1 time account with your bank if it's a large purchase and use a money transfer, that will usually stop any scammers.
Course cash is KING if you're picking up in person.
JMO
Zip.