Hi, I had the same problem with my woodburner here in the UK, I'm not sure were you can get this sorted over in Cat but if you do find somewhere i would recomend getting a price for them to do it for you and if it's not to bad take them up on it as i done mine DIY and it was a pig of a job, I think were the flat head screws on the inside get so hot/cold all the time they are a right pig to undo!

Only advise I can give is have the right size flat head ready and if poss one of them that you hit with a hammer and they twist at the same time (sorry dont know the name of them) and plenty of WD40.

Mine was a very old woodburner so might have been a lot harder than yours?

They sell woodburner glass cut to any size on UK ebay, Not sure if they post to Spain but if not I can give you my UK address to have it posted and I'll bring it over for you in October if that helps.

Sam