Okay, I scanned it last night at 300dpi... and it maxed out my system memory.

I had to scan it in 3 sections because it's so large.
What resolution/size should I be scanning this at, so it would be suitable for vectorization? At 300 dpi 8.5x30" in length, it's upwards of 60MB in size!
Are there any detail/file/compression guidelines I should use for scanning artwork?
Also, what file format should I save it in when finished? TIFF? I'm using photoshop for the scanning.
And last but not least... should I try and put the 3 pieces togeather, or should I leave them apart so the pros can assemble them?
Thanks,
Rook