Ray, if you are pretty sure it is just a seal, and not a failing bearing that is allowing enough shaft wobble to have failed the seal, then a good transmission shop can change the seals without disassembling. Seals like that are standard and the number on the seal will tell you what they are. Get the numbers before the seal is removed incase there is damage.
Since you asked the time, here is the instruction book on how to build that clock !
A great book about seals and the different options available.. Page 81 .. around 5-8 is how they are sized..
http://www.parker.com/literature/Engineered%20Polymer%20Systems/5350.pdf
Seals are available at places like Motion Industries.. or other ball bearing suppliers.