Let's start with the last question. You can program this by hand, but after all that knob twisting and button pushing, you're going to need a psych eval (hi). Everyone has their own opinions about what software is best, but by far, getting started using FreeScan is the way to go. You can always go onto something else later, as FreeScan is, as its name implies, freeware. We host the user guide for FreeScan in the wiki
here
Before you jump into this morass, take some time to read this article from our wiki. Note that anything in blue is a link...you will find links to a page with links to software and one discussing USB connections...
Program your DMA Scanner - The RadioReference Wiki
It's also highly recommended to upgrade your firmware, if you haven't done it yet...
Updating the Firmware in Uniden DMA Scanners - The RadioReference Wiki
Now as to programming Baltimore county - see the bottom of this page, where there are FreeScan screenshots to help you along...
Programming the Baltimore County (P25) System - The RadioReference Wiki
You may need to put the attenuator on to make it work reasonably well...if you have problems, please post them in this thread...
http://forums.radioreference.com/ma.../236945-baltimore-county-p25-fresh-start.html
HTH....Mike