OK, hopefully this method is much simpler.
With colour shot open I went to the "Channels" view (tab under layers on PS)
- I then clicked through the Red, Green & Blue channels to see the Mono views
- Red was too light, Blue too dark with Green being near spot on
- Clicked back to RGB channel. We are now back to where we started when opening the shot. All the steps above were a quick way to see which Channel mix is right.
Step 1) Image -> Adjustments -> Channel Mixer -> Green 100% & click monochrome box
Step 2) Filter -> Sharpen -> Unsharp mask at 100%, 1.0, 0
Gives this shot :-
As the shot was already grainy I don't think it detracts too much from shot....but just in case, here is one run through a noiseware plugin, with a vignette added also
Hope this helps