I have a Nikon d70 SLR. I had this camera completely cleaned and tuned up 3 months ago. Recently I can not take pictures. The battery powers the camera, but the shutter wont engage. An "error" message appears on camera. It has not been dropped or damaged that I know of. Is there any reset button or any troubleshooting advice other than take it to Nikon.

Read the manual on how to do a two-button reset. Also: from the nNikon Support Page on the D70::
It has come to our attention that select electrical components in a limited number of D70 cameras may, in some instances, fail affecting camera performance and/or operability.
While only a limited number of D70 cameras are affected by this advisory, if (1) when a memory card is inserted, your D70's memory card access lamp blinks, locking camera operations and preventing operation, or (2) with no memory card inserted, the camera will not turn on despite the battery indicator showing a fully charged battery, Nikon Inc. will service it free of charge.
To obtain complimentary service for cameras affected by this advisory, please click the link below to download and print the Service Return Form. The Service Return Form provides return instructions.
The Frequently Asked Questions button at the bottom of this page offers more information about this advisory and, should you have more questions, also provides information about how to contact Nikon.
We apologize for any inconvenience you may experience.