Film cameras are not in demand, especially older bodies such as the R4. You might be better off cutting your losses and selling it 'as is'. There is no way in the world that you can have it serviced (by a competent professional) for less than you could sell it for, short of doing it yourself. As an aside, I have an R4 which has had the electronics and focusing screen replaced many years ago and is one of my favourite 35mm film cameras. But I would not suggest doing anything like that now, it's not worth it.

The lenses sound like the grease is a little dry. Again, you're probably better off describing them accurately and selling them as they are. They are not faulty and if some one wants to service them then that should be up to them. Nikon lenses typically feel like they are lubricated with Canola oil, not grease, so they feel very loose. Most Leica R lenses typically feel a little stiff anyway (aside form the internal focusing ones) so maybe they are fine. Have some one else see what they think as your opinion may be biased.

All you need to do is be honest in your descriptions and you will in turn get a fair price.