Hi there Ben,
Sorry, I've only just seen this post. I've been using VSL with Pro Tools since the RTAS version was released in 2007. The first thing to say is that Pro Tools 8 is a brand new release with changes to RTAS and, if I understand correctly, neither VE or VI are guaranteed to work with it yet. Having said that some people report that it does work just fine whereas others have been having problems. Personally I've not upgraded to PT8 yet because VI is such an important part of my workflow. I'll only do it either once it's officially supported or when I've got plenty of time to test it and then, if it doesn't work, to roll back to PT7.3. I'm sure the programmers at VSL will be working on updating the RTAS version as soon as they can.
I'm not entirely sure I understand your first question either - you seem to suggest that you're running VI/VE separately from PT and need to connect the two. You don't need to do this because VI/VE both come in RTAS format which can be run from inside PT. Basically, in PT7.3, this is what I do:
1) Create a stereo "Instrument Track" in PT (must be stereo). Set its MIDI input and audio outputs, if necessary.
2) In the insert slots, choose "Vienna Instrument" (or Vienna Ensemble, but I mainly use VI and from you say it sounds as though this will suit you better too) from the "Instruments" submenu.
3) You'll see a "VSL server" window and in the centre of it there's a button which you click to display the actual VI GUI. Click this button.
4) Now load up your samples and you can now play them with your MIDI keyboard.
As to your second question... Personally I don't import MIDI, I record it directly into PT, adding at least rough articulation switches, velocity info, etc. on-the-fly, although I then edit this and tighten it up afterwards. For me, and I imagine many other people, this is the beauty of the VSL system: the ability to play parts in and hear them more or less in real time. I'm a musician rather than a programmer so I find this more satisfying. On the other hand some people, especially those from classical backgrounds, prefer to write arrangements in notation software and then import them so perhaps that's what you mean. If so then you can do this perfectly well. There are a few approaches to doing this. Perhaps the simplest would be that you set up the VI as set out above and then import your MIDI to a separate MIDI track. Then you set the output of this MIDI track to "Vienna Instrument" (any MIDI channel). This will play back your MIDI part using the samples you've loaded. However what you can now do is record your velocity, expression, volume changes, keyswitches or whatever you use to switch articulations into the INSTRUMENT track. In other words you'll have two separate tracks both sending data to the VI, the Instrument track and the MIDI track. Keeping them separate (at least during the editing stage) might make things easier to manage - but this is a matter of personal preference. The other way to do it would be to copy all the MIDI notes from the MIDI track to the Instrument track and then get rid of the MIDI track. This leaves you with fewer tracks on-screen and looks neater, some people prefer this. You can then record velocity, etc. into this track and you can simply add notes (outside the instrument's playing range) for articulation keyswitches.
Feel free to e-mail me if you'd like me to explain this in more detail. If you're just starting with VI then this probably seems a bit overwhelming as there is quite a lot to learn. But you'll be amazed at how quickly you get up and running; there are just a few key concepts you need to get your head around and then you're up and running.
Hope that helps!
Nick