Will my clock dial look like new after restoration?
That which is called "patina" is actually a combination of age and soiling. If it is uniform, it can be attractive and enhance the value of the item and is best left alone. However, if it is unattractive, or worse if it is contributing to ongoing deterioration (which is usually the situation with painted clock dials), then removing the soiling is a necessity. To put new paint and sealant over soiled paint would be inviting trouble.
It is often amazing how much filth comes off of a soiled clock dial during cleaning. If your dial is a manufactured item, the paint was white when it left the factory. Typically after cleaning and during restoration the paint will be found to be an off white, due to the age of the paint itself. The color of the paint to be added has to be matched to achieve uniformity with the original, existing paint. If your clock is a calendar clock with two dials it is essential that both dials be cleaned so that there is uniformity in their appearance.
In a finished dial restoration the dial will look whiter and brighter overall, but it will never look pure white due to the paint itself, which is very aged. In other words it won't look "like new" (which would not be desirable,) just very clean with all its defects removed.
A good dial restoration should be as undetectable as possible - not that the intent is to deceive, but the goal is to arrive at an aesthetic balance that is pleasing to the eye, has corrected all the deficiencies, and most importantly looks like it would have had the dial not fallen into the deteriorated state that it did.