Wow - how do I follow that!? First off Seb really knows his stuff, but don't tell him I said so or he'll get an ego. Here's my take:
Getting a DSLR is like opening Pandora's box. If you don't want to deal with any computer related stuff (probably not the case or you wouldn't be here), then it's not for you. You'll learn things like not sharpening in the camera to have more flexibility later with Photoshop, etc. Of course, you're setting yourself up for doing more work but getting better results. Essentially, you become your own lab. I don't make my own prints, but shoot, edit and prepare the files in Photoshop, then burn a CD. The lab doesn't do anything to my files other than print them - no "optimization", etc. Works out good for me for not having to own and maintain a nice printer, but some day I'll have to get one. I will tell you that I've probably paid for my Fuji S2 in film and processing costs since I got it last August - plus the benefits from instant feedback but that's enough of that story... But, by the time I add in all the money I've spent on compact flash cards, Photoshop CS, Monaco Optix monitor calibration software, etc - I don't know if that holds up.
Compact flash cards are necessary, they're essentially "digital film". It's what your images are recorded on. I personally use 512mb cards (you can download a card and burn directly to a CD), but it depends on how you shoot as far as how many and how big they need to be for your situation. A typical day's worth of shooting capacity is usually fine, but what about vacation for a week? Something to think about. With digital, it's all up-front costs.
The D70 is compatible with the SB50DX, but not the most current flash system they offer. Nikon's newest iTTL flash system looks pretty good, but you'd need an SB-600 or SB-800 with a D70 or D2H to use it. With a D70 and SB50DX, you might get the best results shooting in "A" mode on the flash, nothing to do with TTL. Books could be written about this, but it seems to be the concensus.
For film cameras, you can spend A LOT less up front and get a really nice camera. How many rolls a month do you shoot? How big are your prints? How fast do you need them? These are all questions to ask. I don't have any personal experience with the N65, N75 and N80, although my Fuji S2 is built on an N80 body (sort of franken-camera).
We just need to get you out of auto mode once in a while...