Ron--
I'm not familiar with the book you reference, so I don't know where exactly your knowledge base lies. The making of inkjet negatives has also become more refined in the past 11 years, but here are some basics.
Let's assume for a moment the following conditions: 4x5 original negative, 12x15 desired final output (3x enlargement).
It is generally accepted that the minimum pixels per inch you need for an output to look reasonably sharp is 300 pixels per inch, though visual differences can be apparent up to about twice that, given very sharp source material. 300 DPI is typically the native output resolution of Canon printers, Epson are typically 360 ppi, and both typically have a mode that can print at 2x the native resolution, as well. Don't be confused by the 2880 dpi or 3600 dpi or whatver specified by the manufacturer. That's the minimum precision of individual ink droplets, and it takes more than 1 ink droplet to form a given color pixel.
So let's settle on 300 DPI for your output device. You can re-do the math depending on the specifics of our output device. That means you need a digital file that is 3600 X 4500 (12*300 X 15*300).
In order to get a digital file of that size, you need to scan at 3600/4" (negative size) = 900 PPI. That is within the range of any decent flatbed scanner capable of scanning transparencies. I would recommend scanning slightly above that resolution and scale down. But make sure you scan at a native resolution of your scanner. e.g. if your scanner is a 4800 PPI scanner, you can scan at 2400, 1600, 1200 (4800 divided by 2, 3, 4).
Hope that's a good start for you.
There's plenty of threads here and other places about which printers to use and how to adjust your images to account for the non-linearities of the printer and your process (aka "creating curves").
Good luck--
Greg
