Difficult to work on? No.

You can get performance parts for them

http://www.firmfeel.com/fmj_body_mopar_parts.html

There is some disagreement as to it's abilities to handle at the limits.

I think for anything on the street it can handle as well as the limits of the driver.

If you are junkyard picking later model Diplomats and Gran Furys were used as cop cars, a lot. The fender tag code is AHB they typically have the sorted out HD parts and added handling goodies, like rear sway bars.