The DS-70P that you plan to use does not record the full range of audible sound. It records roughly 100Hz - 15kHz. The full audible range is roughly 20Hz - 20kHz. As a result your recordings will lack a bit in the low and high end. You can still get a decent sounding recording, but you will notice the difference if you compare it to a recording made with a better mic.
If you are a bit handy with a soldering iron, I would try building the Greenmachine DIY battery box (see the Live Recording section of
www.minidisc.org/forums). It will cost only about $10-15US in parts, and will serve to power your mic. If you go DS-70P > DIY BBox > Line In you should be able to get better results than you would with DS-70P> mic in. Make sure you set your levels to manual on the MD and turn AVLS off. Save the money you would have spent on a pre towards a better set of mics.
Good luck and happy taping!