As a replica watch arrives, the movement inside is not "factory fresh." It is either used or has been stored for an extended period in a non-sanitary factory environment.
All mechanical watches require a complete dis-assembly, cleaning, examination for worn parts, re-oiling (in the proper amounts!!)
and final assembly, and testing for water tightness every five years
Why? The oil inside every mechanical watch slowly evaporates and turns to gum over time, if you use it or if you do not use it. This does not matter.
Now, knowing the replica watch you just bought has a dirty or dry or possibly over-oiled movement your first job is to protect your investment and have it serviced. When that is done, you will have a watch which keeps excellent time and is good to go for another 5 years.
Modding is done by a skilled craftsman who can do any number of things to a watch. Scrape off the poor Chinese luminous material and replace it with genuine Swiss lume. Re-shape the basic case of the watch to make it appear more genuine. Add swiss-quality anti-reflective coatings to the watch crystal. Remove Chinese parts and replace them with genuine parts from the actual watch the replica is trying to emulate, like dials, hands, straps .. etc ..