use that .avs script
only in Premiere when rendering the final amv, but the Low Quality version doesn't need to look good; it just needs to be able to generate fast previews for editing, so it doesn't need to be filtered [which is what's slowing things down

]. What matters is that the two versions of your footage are frame-by-frame the same, regardless of quality. The difference is that one is Low Quality [but has fast previews... and is really easy to edit with], and the other is High Quality [but is really slow for previewing/editing/rendering]
to make your Low Quality version, comment-out unneeded lines so they don't have any effect [with a #], and render it under some low quality settings with PICVideo's codec
mpeg2source("G:\Pita Ten 3.d2v")
#ConvertToRGB32(interlaced=true) <---probably don't need anyway
SmoothDeinterlace(tff=true, doublerate=false)
ConvertToYV12()
Crop(8,0,-8,-0)
LanczosResize(640,480)
#deen("a3d",4,12,14) <--- see below *
#SSXSharpen(ssw=4,ssh=4,xthresh=255)
#Warpsharp()
#Tweak(cont=1.1,sat=1.5,bright=0.1) <--- see last note **
#ColorYUV(gain_u=11) <--- see last note **
It still might take a couple hours, but much less than 3 days

[you might want to check out Vdubs Job Control, especially the feature that automatically turns off your computer after it's done rendering, which is excellent to have your computer render over night... then the next day just turn on your computer, and your files will be ready for you

]
Anyways, when your LQ version is ready, Edit your amv with it, and when you are done, you should be able to swap your LQ .avi file with the HQ .avs file in Premiere using the method outlined in the guide. [test if it works, before making your entire amv, and get comfortable switching back and forth between the LQ and HQ versions] Using this method, even slow computers can edit at lightning speed... unless you are doing a lot of effect-work.
*Just to mention, you might want to tone down deen(), warpsharp(), and tweak() so it's not overfiltered... and I would probably put ssxsharpen() after warpsharp().
**Also, it might be safest to do color adjustments during post-production, just in case your export settings don't allow for the new color range.