You aren't exactly 'screwed' but you might want to change your mind about about setting it to standard 4:3 and go with the widescreen format.
To convert wide to standard you have to chop off the right/left side(s) and then zoom - we all know what 'zoom' does to graphics - pixilation city.
To convert standard to wide you chop off the top/bottom (or a bit of both) and just leave it - it wont pixilate but some scenes will look like the cameraman was zoomed in a little too close. And on a true widescreen TV the right/left sides will show a black border.
The video can be saved with your elite skills in post production and scene selection - and with some good luck in that the video shot in wide screen was shot well, and has a lot of usable shots. Then you only have to convert a minimal number of scenes from the video shot on standard - You can just use the ones where you were 'zoomed-out' and minimal content will be lost when you slice off the top/bottom.
If you don't have very good shots from the 'inexperienced' cameraman, then you might consider a mixed presentation - using the wide shots sparingly and artisticly - ie the songs are all presented widescreen and the rest of the drama is not. Then when someone asks, you can explain the virtues of 'dramatic effect' or artistic license'
As for the capabilities of Premier 6.5, I cant answer to that as I have never used it.
My System Specs:
Cameras: 2 x Canon XL1s
Computer: Dual Intel Xeon 2.8Ghz processors (hyperthreaded) - Intel SE7505VB2 mother board - 2 Gb PC2100 RAM kingston -Adaptec FireConnect 4300 -2xseagate 10K scsi hdd 150G ea -2xseagate 7200 ide hdd 200G ea - Plextor PX-708A DVD burner - ATi Raedon 9800Pro video with Dual SUN 21\" monitors - Sound Blaster Platinum live!
Software: Windows XP Pro with SP2 - Pyro Pro (adobe\'s premier pro, encore DVD, and audition bundle)