I have an Icom 5100, it is a very useful FM/D-Star radio. However, the trade-in value to a dealer is very low… there is little demand for them.
Personally, I would look around for one on the second hand market. Note they mostly didn’t come with anything to mount the head unit, not even on a desk, you can fairly easily make a mount but beware of the price Icom charge for them.
A programming lead is a straight jack plug to RS232 lead, the wiring diagram is in several Icom manuals. The Icom programming software is free and straightforward to use.
73 Dave