We have the same fault on an SL of similar age.
I quoted customer for a new unit, the customer got onto google and found a place called Broadspeed who said they could reset the counter. Nearly a month and loads of phone calls later they told him they could no longer do it and sent the unit back. The customer then brought a device off ebay that was supposed to allow you to reset the counter yourself ( a bit like eprom programming) but all this served to do was kill the unit completely.
I'm sorry I've been no help at all other than to let you know the pitfalls we had.

Regards,
Steve