Hi Colleen! Welcome to the forums!!
I'm a total newbie so bare with me.
And not only will we bare with you, we'll bear with you as well!!!
Your computer is fine for editing and playing HDV, which is the easiest of the high definition formats on computer resources. (Good thing you didn't go for an AVCHD camera... I am a HDV fan myself, and use your new camera's predecessor, the HV20, which does an excellent job.) You won't need to use SmartProxy either ... though bear it in mind if for some reason editing HDV in normal mode gets too long. Be aware, though, that generating the proxy files, if you use SmartProxy, can take a very long time in its own right, and then applying the proxy edits to the real files will also take time.
But if it is any use, I have just been doing a HDV project on a Pentium 4 much older than the Core 2 Duo you have It has only 2 GB of RAM; and it edited it just fine as is. No SmartProxy or other tricks necessary. The extra RAM you are talking about would be useful, but not strictly necessary. But it is very cheap these days. Be aware, though, that with 32 bit Vista, it can only see a maximum of 3.5 GB RAM.
When it first came out X2 (and VS 11/11.5 before it) had a problem exporting a finished project back to the camera. (The command in VS is Share > HDV Recording.) But with the patch, it works just fine. Again, I know, because I happen to use that command all the time. To get into a little video geek-speak, the HDV camera films in high definition mpeg-2 but in the Transport Stream (TS) version of it. When captured, it is converted to Program Stream mpeg-2. There is no great difference between the two types that is worth going into detail about here. But to export back to the camera, it has to be converted back to Transport Stream format. Share > HDV Recording does that for you.
What it does is do a full conversion of your project to TS mpeg-2. That creates a complete new file, which you can play on software DVD players capable of playing high definition video such as PowerDVD 9 or WinDVD 9. But when it is done converting, a little screen comes up. You have to have your camera connected via Firewire (as you do when capturing from it), and switched on in PLAY mode. Then the program asks if you want to send the video to the camera. And you let it do its thing (as long as you have an empty cassette in the camera of course!) The quality is superb and it is an excellent way of watching your edited HDV on your TV. I would say, though, that it would be much better if you had a HDTV to connect it to, because then you could use the camera's HDMI outlet to connect to the HDTV's HDMI input for the highest quality playback.
I no longer bother exporting back to the camera, frankly, but I use the Share > HDV Recording workflow all the time as I think the product is better than that if you just went Share > Create Video File > HDV. But either way, it is already in a format ready for storage on an external drive.
In point of fact, I store all my edited HDV on an external hard drive, just for safety's sake, as well as on one of my editing computer's (six) hard drives. But I can connect that external hard drive direct to my Sony PlayStation 3 (which is an excellent and very versatile Blu-Ray player in its own right). The PS3 is connected to my 46 inch HDTV also by HDMI, and the PS3 detects all multimedia on the external drive and plays it superbly in full high definition. In fact, you can even put your edited video on a large enough USB memory stick and it will play on the PS3. Furthermore, I have the PS3 networked to my home network. Using Windows Media Player (or Nero Media Home) as a server, the PS3 can play all my multimedia, including the edited HDV and AVCHD, direct from my computer to HDTV. As I say, it is versatile!
So there's a few things to think about, just to get you going!!