1) Buy replacement glass, either from a junk yard (there are a bunch out there) or an auto glass shop. Most shops can get it for you new, though not all of the new glass fits as well as original windshields, and it tends to be much more expensive. 2) Buy new rubber. If you are going to put the effort in, it's best to replace the seal as well. The "Classic Cal" look (all black) is a good way to go. Many people think think it looks better, plus you don't have to fool with inserting the chrome trim into the rubber - a serious pain. 3) Remove the old glass. Use a utility knife to slice off the outer edge of the seal, running a thin blade between the glass and the seal. Pull out the glass and chuck the old seal. As you cut away the old seal make sure not to let the widow fall out. Use this step as well if you are removing the glass yourself at the junkyard. Preparing the Frame and New Glass 1) Inspect your frame. Those rubber seals, especially if they are old and cracked, can trap water against the metal frame which leads to rust. If the frame is seriously rusted, it is time for a trip to the body shop to get a new one cut in. If there is light pitting, a sanding, filling, priming and painting is in order. Make sure the surface, even if undamaged, is clean and smooth so the new rubber will seal well. 2) Clean both sides of the glass. 3) Put the seal on the window. This is trickier than it sounds because the new rubber is a tight fit. Find a large flat work area and put down either a rubber mat or thick cloth to keep from scratching the glass while you are working. Starting at one corner, begin sliding the glass into the inner groove of the seal (they make special tools to facilitate this, but a blunt screwdriver will work well if you are careful). A second person here is helpful to hold the seal on the glass while you work. 4) Have patience - lots and lots of patience. Remember, don't over torque the glass putting the seal in place. Doing so is a good way to end up buying more glass. Work slowly and make sure the rubber is well seated on the glass. Lubricating the glass with a little water mixed with dishwashing soap can make the rubber slide onto the glass more easily. 5) Prepare the seal and window or windshield to go back on the bus. Get some nylon rope a little thinner than a pencil and long enough to go all the way around the window with enough left over to hold on to - about 6 inches to a foot on either side. Again, soapy water can help here: Starting at the bottom of the window and leaving some excess rope hanging out, begin inserting the rope into the groove in the rubber seal that will seat into the window frame on the bus. Run the rope all the way around the window seal in the groove and leave the excess dangling from the bottom. Windshield Installation 1) Lube the window frame with soapy water,and have someone outside the vehicle press the new glass and seal up against the frame with the bits of rope hanging on the inside of the bus. Line up the glass (This is especially important with bay window-style windshields, because the curved glass has to fit the frame just right.), then have the person outside the vehicle press the glass firmly into place. The second person on the inside needs to grasp the rope and begin pulling inward. That should pull the inner lip of the rubber seal over the edge of the window frame and begin seating the window to the vehicle. As you pull the rope towards you inside the van, the window should suck into place. Make sure the person outside continues to apply firm pressure and keep everything lined up as the person on the inside pulls the rope towards them. Again, there are special tools that do the same thing, but rope works well and is just about free. Have a thin putty knife without sharp edges on hand to help with any trouble spots or snags the rope may hit. 2) Inspect your work. Once the last of the rope is out and the window is in, make sure the seal is in place all the way around. Fix any areas that might have folded under with the putty knife by running it between the frame and the rubber. Press the window firmly from the inside to make sure it is well seated, but make sure your helper is ready to catch it on the outside in the event you pop it all the way out. 3) Clean the glass and seal. Maybe even treat it with rubber preservative so you won't have to do this again too soon. 4) Buy your helper dinner. They earned it, and saved you a bunch of cash. A lot of glass places will charge upwards of £100 just for the labor (that's with you supplying the glass and seal).