No problem Steve, I can help you out with the rules and regulations around here.
To start with:
Register and get a membershipcard over at
http://www.nabv.comTo own an airsoft gun (or as many as you like), you are required by law to have a membershipcard of the Dutch airsoft association. When applying for a membership, you will have to be registered at a Dutch address and, through the registration system on the website, apply and pay for a certificate of good conduct (VOG).
It takes between a few days to a few weeks to receive the certificate of good conduct from the ministry of justice. When it's in, you have to send the original to the NABV and pay for a full membership.
You'll get your membershipcard within a few weeks.
Most of this is automated on the NABV website and I can help you with it if you'd like.
When you have the membershipcard you are allowed to have as many airsoft replicas as you like as long as they are <3 Joules and 6mm, 8mm is not allowed. Same for launchers and replica grenades and so on.
You do not have to register your airsoft guns. You have to store them in a preferably locked closet so that they can not be considered threatening to others.
You can buy airsoft guns all over the world, however, make sure the seller has a copy of your membershipcard and puts that inside the package for the customs to see. Without it you risk being charged with the import of illegal weapons. Only when the package is shipped to the address that is on the membershipcard, the customs will let the package through.
When transporting your replicas to an event in the Netherlands, make sure you print the invitation to the event, which can be found on the NABV site and have it with you, together with your membershipcard and ID card or passport. All Dutch events have to be reported to the NABV and you can find them on the website. Some events require you to sign up on the website of the event host. But always let the NABV know you're going by signing up and printing the event info on their website as well.
The replicas are to be transported in a preferably lockable case.
Keep in mind that any visible weapons during transport can lead to the police aiming weapons at you and yell not too pretty things at you.
[EDIT]
As for your question. AEG's are illegal in Germany. All airsoft guns have to be singleshot only and have a stamp on it to prove it (it's a little S inside an octagon). Sending an AEG to Germany is a risk I'd not take.
When you comply to all of the above you can just have it sent straight to your front door.
To have it in The Netherlands you'll have to comply to all of the above anyways.