Here are lots of generalisations:

With my experience of film scanners I've found that colour negs generally scan better than slides - they certainly have a much longer scene tonal range, and allow more tweaking. A film scan with a desktop scanner can bring things out of a neg that you won't see in a machine print. That's just my opinion, of course.

Personally I wouldn't bother to use Vericolor slide film - it's been discontinued anyway, though there seems to be plenty of stock available. I'd say that it was much easier to learn how to do a good neg scan than to learn how to use Vericolor properly, but that's just my opinion. This isn't a digital forum, so I'll refrain from going any further on the subject. However, it is a C-41 film, so it can be developed at the local one-hour lab.

When you refer to scanning 8 mm movie film, do you want frame grabs or full motion?
If you want full motion then transfer to DV (or now/soon HDV?) might be the best answer - either by a standard projector and camera 'film chain' with contrast control or by a dedicated 'Workprinter' - a modified projector. All kinds of variations are possible (cutting blades off your projector's shutter, filing out the gate...).

For still frame grabs I prefer to copy the Kodachrome to a good 35 mm neg film, in which case the whole tonal range of Kodachrome can usually be captured. I wouldn't use E-Dupe - can't see any need in this case. I know that other people just scan the film, and get good results - but even 4000 ppi doesn't give you much from one of those tiny frames. Depends on what you want for your final resolution. Kodachrome can be a bit more difficult to scan than E-6 films, mostly because of the higher D-max in my opinion.

If you can afford it, you can get it done at a good telecine house. I guess that the charge would be in the order of 300 to 500 dollars per hour. Multiply your film running time by three to get a rough estimate for the basic time required. Buying your own 'Workprinter' begins to look attractive.

You could shoot on 8 mm colour neg instead of Kodachrome - but I don't know which camera you have. With Standard/Regular 8 you should be OK (if you can get the reperforated stock) but not all Super 8 cameras will run neg film flawlessly. Super 8 neg stock is a lot easier to get than Standard 8 neg stock though.

There are just so many variables that it is difficult to give a good answer. Good? Quick? Cheap? Pick any two. As usual.

Best,
Helen