Its pretty easy to dismantly the headlights - you just have to have the balls to put them in them oven!!!

Basically, you remove all the fixings from them, remove the glass retaining clips, then bung em in the oven for 10 mins until the sealant becomes pliable, then the glass just pulls off!
I never had the required balls to do it to my PD, but I have to on the scoob to de-tango the headlights. Scarey stuff!!!
Personally speaking, I would avoid 'universal fitting' ones and try and find some specific ones that use standard wiring etc.