Should work, as long as the 250R lamp housing has the same kind of hermetic seal. I took apart the housings on my Stratus Coupe to paint part of the insides anodized red, and it worked great. Went to do something similar with some aftermarket clear tails for my Neon, and they didn't come apart, because the two halves were glued together, not hermetically sealed like the Strat headlamp housings.
The thing is, they are hermetically sealed when they are glued together, that is why you need to bake the headlight housing so you can melt the glue and take the parts apart.
The guide is for a different bike, but it should be no different on a 250R.
Those projectors are too long to fit in the 08+ 250 housing without modification. I put them on my 08 and I had to enlarge the openings in the reflector so the projectors are sunk in more. Even then the lights barely clear the lense cover after aiming them. If your not good at modding stuff to work I would not recommend them.