ᐅ Painting, varnishing, or replacing wooden windows and interior doors?

I need some experience and tips again on the topic of "refreshing old, dark windows and doors."
The door leaves and frames are real wood veneer, and the window frames are solid wood. Our building inspector said that technically everything is fine and replacement is not necessary, so we want to keep all components.

The goal is to make everything light (white, light beige, for example), which is obviously much cheaper than replacement. Is this something you can realistically do yourself, or is it better to hire a painter or carpenter?

Does anyone know roughly what this costs per door and window?

Thanks!