A2steve you may find the front one a bit of a mission due to the tight space and dash in the way, ive done many of these over the years and its not that hard, i think its just a black pu sealer they use and also to make life easier as mentioned earlier extend blade out a few inches and keep it flush , flat to the glass, masking tape so the tip/cutting edge does not to scratch the glass..
katie if you or a friend is brave enough you can fit the glass yourself for about £10, its not hard at all just go slow and be carefull not to cut yourself on the broken glass, advise wearing thick gardening gloves. all you need is some fine wire wool, 2" masking tape and a tube of tiger seal
http://www.ebay.co.uk/itm/TIGER-SEA...577?pt=LH_DefaultDomain_3&hash=item2355503a81
Bassically clean off the glass with the wire wool so no old glue or gunk , wear a mask or be carefull not to breath in the dust
break away any left over glass around the edges as best u can then use a stanley knife carefully same process as i explained to steve to remove old glass , it dose not matter if theres any black sealer left around the edge if under say 1mm as wont hurt saves digging into the paint on the edge too much , then clean off the lip and arround where the glass fits and wait till dry. then put a bead all the way around in the center of the lip , say the size of a micky dee's straw and gently push the new glass into place , youl notice the tiger seal will spread evenly once its about right check n wiggle about so it matches how the glass fits on the other side of the car , gaps , location ect and then just tape arround withe the 2" masking tape , leave this on till the next day and your done all fixed, just one note take a white peice of paper out to the car open a door and hold on one side of the glass as may be clear or tinted and check the one steve has is the same as it will look really bad if its wrong and stick out like a soar thumb , anyways good luck
Gary