I ordered the speedometer from Bridgeville Auto in Bridgeville, Del. It was $85 including the shipping. I ordered on Friday midmorning and had it at noon today, Monday. It was very well packaged; double boxed with packing material around and inside the inner box. They sent the whole cluster. It only had 64,*** miles on it. The needles are that nice deep orange/red. It looks like a new one. It took me a little less than an hour to pull the old one and install the new one. Everything works great, including the rheostat or potentiometer, the clock, all lights and gauges. My temp gauge is not bouncing around like it was. It would jump up to just under 100 and back down to 85 and stop in between sometimes. Now it is registering the same temp as my laser thermometer does when pointed at the housing (at least within a couple of degrees).
Thanks for the help. It is great to get so much good advise and the heads up that only someone who has done the procedure before would know. I thought it was the speedometer itself since the odometer still worked, but it is reassuring to get one's diagnosis reinforced.
Thanks to all who responded. Sorry for the long post.

__________________
Mike

2000 SL500 22,000 miles
1981 300CD 188,000 miles
1979 450 SEL 266,000 miles
2005 Cadillac CTS 25,000 miles