do I need cv joint of driveshaft?

my 120k mile 10/2000 x-reg merc vito 108cdi suddenly developed a severe and rythmic 'knocking' that continued when I depressed clutch and freewheeled. I limped home and raised front wheels off ground on full right steering lock and spun the wheels. The nearside wheel produced a noise on every revolution, the offside did not? The gaiters and boots all look intact. oddly though, the knocking noise did not seem evident when driving in reverse? If it is cv joint or driveshaft, are they particularily difficult to change out, and do I need special tools?