Non-technical people are often intimidated by electronics, but conversely, we techies might feel equally at a loss faced with an intricate clock mechanism. In fact, stripping down, cleaning and reassembly of a relatively simple clock such as a mantelpiece carriage clock is well within the capability of anyone prepared to spend a little time and to take reasonable care. A carriage clock is an excellent introduction to clock maintenance as you can see all the working parts. After a number of years the oil on the bearings will have evaporated or congealed, and picked up a surprising amount of dirt. At this point it will no longer run for as long as it should, or even run at all. A service clean should return it to good working order.
A fully or partially wound clock spring stores considerable energy. Its uncontrolled release can cause serious injury and considerable damage. Always unwind the spring before starting work. Never attempt to replace a main spring - this is a hazardous operation best left to an expert.
Only ever use specialist clock oil. This has sufficient surface tension to keep it where you put it, leaves no residue as it gradually evaporates, and doesn't attack any lacquer that might have been applied to brass parts. Only use specialist clock cleaning fluid for cleaning the various parts. There are two types of this: Ammoniated cleaning fluid is tough on dirt and grease and removes any tarnish, bringing up brass to a lovely shine. On no account must it be mixed with or contaminated by other cleaning agents as some combinations can generate highly toxic fumes. However it has a pungent smell and must be used in a well ventilated area. It can also cause stress fractures in brass and so parts should not be left to soak in it. Only ever buy it in a plastic bottle as it may cause a tin to leak. Non-ammoniated cleaning fluid may not be as powerful but is safe to use, and is certainly to be preferred for rare or potentially valuable clocks.
The website of the National Association of Watch and Clock Collectors includes forums which are a mine of information if you have questions, perhaps because your clock is not exactly the same as mine or if anything is not quite clear.
I was encouraged to service my 35-year old carriage clock by a blog posting by Braintree Clock Repairs (a site well worth browsing). This guide owes much to that, coloured by my personal experience and salted with wisdom from amateur horologist Phil Harris.