It's not difficult at all Terry. Reason being, the leds come pre-installed in housings "festoons" that are the same size as the factory halogen bulbs. However, if they don't have built-in resistors already, it's recommended to solder some in, and that could be some work.
1998 BMW 328is - summer
1994 BMW 325i - daily
1992 BMW 325i - gone
1988 Mercedes Benz 190E 2.3-8V - sold