Not hard just a little fiddly. I was lucky as I had just bought some little interior LED replacment bulbs from Banshee. Each bulb had 3 tiny high intensity leds, only a couple of mm across. Once I had dismantled one of these, I then stripped the coming out of all the electronics, and removed the plastic PCB to fit the leds. I then soldered and heat shrinked some jumper cables on, and these were then slaved into the PCB once I had refitted it.
The LCD display was stripped down and the orange diffuser removed, a custom one then made and inserted and then the whole thing reassembled.
Time consuming but relatively easy as long as you are happy with soldering, multi-meters and some delicate disassembly/assembly.
The needles are now white with red tips. They are the needles off the R25 with the tips painted as I wanted to get rid of the orange theme totally. They look dim in the pictures as I had to step the exposure down to stop glare from the lights as there was so much contrast between the dark and light. They are much more visable in reality.