fitting windows is a doddle first remove any sashes/openers then with a glass cutter score the glass into managable sizes on the opposite side of the scored glass gently tap on the score mark this will break the glass do this until all glass is removed by the way wear a good pair of safety gloves when doing this.now your frame is ready for the next stage with a saw cut out any mullions or transoms when this is done all your left with is the outer frame using a stanley knife cut between frame and your plaster reveals(thats the bit on the inside of your house surrounding your window).once again with a saw cut the outer frame on the vertical jambsits easier to make two cuts on each side approx two inches apart with a chisel knock out this little piece this gives you somewher to put your nail (crow) bar now just prize the frame out doing it this way will save you damaging your brickwork.this is not a difficult job anybody that can use hand tools safely can do this just remember the less mess you make taking the frame out the less you will have to do when your new window is in. 
