Hi Hans
I will try the best i can to reply to your questions:
No, it is not possible to watch 3D on your current Beovision. The 3D requires the new and improved BS3 (not to mention a 3D capable screen).
Yes, you can connect an airport express directly to your BS3, but there is no dedicated audio only input. I other words, you have to connect it so say AV4, and then assign say "v.mem" to AV4. When you then want to listen to your music on your Lab5´s, you press "v.mem". The thing is, that this will also power up your screen without you having anything to show on it. Dont you have a dedicated audiomaster connected to the BS3 through Masterlink?.
Another option is using an AppleTv2, this connects through HDMI to your BS3, and works as an mediacenter (with quite a few limitations here in denmark to be honest). By doing this you can have the cover of the album your are listening to displayed on your tvscreen while listening to your music. And you can even control it by using your B&O remote.
Furthermore, the AE is not something you startop, it is just an adapter that is always running. You have to turn your TV (or BL5´s if connected with spdiff directly to AE) on by using your B&O remote.
Third question can be answerd the same way as above. No the BS3 can not by itself turn on anything. You have to do this using your remote.
If you can tell me exatcly what B&O products you have and exactly what you want to achieve, i will do my best to help you on the way to what in my opinion would be the best solution.
Regards
/Ehlerz
BV7-40 MK IV, BL5´s, BL3´s, BL 3500, BL7-4, BS3000, BC 6-23, BV 1, BS3.