You need to spend £20 - £30 get the right tools for removing screen, like these
http://www.drapertools.com/draper/templates/draper/details.asp?newrecordset=yes&classlevel=39It can be an easy job, or it can be a right pain, 50/50 depends if its really bonded in well after a replacement screen. Rust probably caused from an incabable autowindscreen guy anyway.I've never seen my mate struggle (to much) with windscreens when spraying. Puting them back in is easy.
A bodyshop will be more than capable of removing it though. A few years ago my Mondeo ST200 had a replacement screen fitted by Auto windscreens at work for stone chip, I kid you not it took him 7 hours to remove & re-fit, I had glass everywhere (down back of dash, etc) and scratches on the bonnet because he never covered it. I very nearly smacked him and so did one or two lads at work, cos they liked that car.