You may not have to disassemble your dash, depending on your dexterity but certainly the panel under the steering column has to come out if you are to remove the clock.
I have read $125 for quartz replacement. It may be worth that to you depending on the general condition of your coupe and wallet. Getting the works out of the can the clock is sealed in, is not for the faint of heart. In my case I have two, so little to lose.
I was able to muck with (technical term) my spare clock on the kitchen table and voila, it worked. Don't really know what I did, maybe it always worked and only needed juice. Maybe it was a connection thing, maybe it was flattered by the attention, maybe it feared my "nothing to lose" attitude, maybe it was a secret member of some Anti-vivisection organization.
Be sure your clock has power and ground before messing with it. Also check that the lights illuminate the clock when the headlights are on, although lights won't mean the clock will work.
For me to remove/replace a clock requires my XL hands getting up under the dash, generally as follows.
Each round instrument "group" is held to the dash wood by two knurled nuts on studs which project forward from each group. If you can snake your hand up and in, unscrew those nuts, and the group can be rotated about "1 hour" in one direction (forget which) and it will release from the wood. Then you can lower it and disconnect the wires. For the clock there are I think three wires: power to clock, ground, and power to lights. Installation is as they say the reverse of removal.
If you search out a picture of the instruments (such pics are on this list), you'll see what's involved. See post number 278 and a few following here:
http://www.e9coupe.com/forum/showthread.php?t=17735&page=28
