1997 Jaguar Vanden Plas throttle linkage

Engine Mechanical problem
1997 Jaguar Vanden Plas Two Wheel Drive Automatic

My wife's '97 Jaguar Vanden Plas has been acting up recently. When the engine is cold - especially in colder weather - the accelerator doesn't respond at all. The throttle linkage seems to be frozen. ( We live in South Florida, so "cold" is a relative term ). Once the car gets up to running temperature, the situation seems to resolve itself; although the throttle does seem to stick sometimes while driving, so it becomes necessary to sort of 'kick' it loose. Not very safe. How do I clean and/or lubricate the linkage ( if that's what's required )? And how difficult would it be for me to replace the throttle assembly, if necessary. ( I'm minorly to moderately mechanical ). Thanks; and Merry Christmas.