The Programming Cable: Many vendors on eBay and the like will supply a Motorola GM340 already set for you, what they will need to know is the frequencies you intend to use, the CTCSS codes and the setting in fig2 below.
However, it is obviously best to get a suitable cable to connect the Motorola to your PC and do the job yourself.
You are going to save yourself a lot of trouble with drivers etc. if you buy one which has a FTDI FT232R chip already built in. You can buy one from a number of vendors on eBay of course. The one I bought from Mark Dunkle KJ6ZWL { dunklem@gmail.com } has worked fine for me, and he also provides a high level of support.