I had an "oh shit" moment a few months ago when my BB broke and I couldn't tether it any more. So, I got tethering via Bluetooth working to get around it. So the short answer is, yes this works. However, I've found the connection to be more unstable and not as fast as using a real cable. But, it does work sufficiently enough for most purposes.
I also have a Dell laptop, so here's some quick tethering instructions:
- turn on Bluetooth on device
- launch Bluetooth Settings
- Click New Connection
- Choose Express Mode, Next
- Make sure device is shown, click Next
- Type any 4 digit number for PIN on device
- Retype same PIN on computer
- "Accept Connection" on device
- Click Next, set up your connection as you would any normal BB dialup.
Don't know the answer to your sync question (get a BES).
Regarding your third question, I think you need to spend 30 seconds researching the answer. You can get a Bluetooth USB adapter for your desktop for under $10.