I'm assuming from your screen name that your talking 'bout a 69 bug?
I'm not sure about the seals, but I think you do have to remove the wiper assembly to replace them.
On the windshield seal, it's EASY to replace yourself and YES, the glass will survive. Even if for some reason it doesn't, a windshield for a 69 bug is cheap. Do you want to put back an original "American" style seal (has the stainless trim in the rubber) or Cal-Look (just the rubber with no trim)?
The best way to do it is to cut the glass out of the old seal using a utility knife. Once you have the glass out, remove the rest of the seal and clean up the area where the seal goes. Take care of any surface rust now, while the seal is out.
To replace the seal, get it warm by laying it in the sun, or heating it in a microwave oven . . . be carefull though. You just need it warm. You don't want to "cook" it. With the seal warm and plyable, carefully put it on the glass. DO NOT use any lube of any kind while you are putting it on the glass. I try to put the seam where the seal is joined together at bottom dead center of the windshield. Be careful when you are trying to pull the seal over the last corner of the glass. It'll be a tight fit and if you get in too big a hurry, the glass might not survive.
Once the rubber is on, put in the trim if you're using American style rubber.
Now you are ready to install the glass. If you ask 100 people who have installed glass in a VW, you'll probably get at least 75 different methods, but when you step back and look at them, they are all pretty similar. Here's how I do it . . .
I use heavy monofiliment weed eater cord if I have any. If not, 14 or 16 gauge automotive wire works pretty good. Wrap the cord around the seal inside the grove where the lip of the body goes. I wrap the cord around all around the glass and overlap it on the bottom so that I have the ends of the cord hanging out at each bottom corner. You will need some lubrication to intall the glass into the car. Some folks use dishwashing liquid, some use WD-40, some use light oils . . . everybody has their favorite that they swear by. My favorite is K-Y Jelly. Don't laugh; it works! Some people soak the entire grove with their lube of choice. I've found that "less is more." I just lube up the back of the seal and rub a little around the edge of the body lip. With the seal lubed up and cord installed, set the glass in place. Make sure it's centered and make sure your cords are hanging out inside the car. Carefully push it back in place as far as you can. Now, you need some help. I've done it by myself, but it's easier with help. Start in one lower corner and pull the string across the bottom of the lip while you helper keeps it press snuggly against the body. As the cord pulls out of the seal, it'll pull the lip of the rubber over the body lip. Keep pulling the first end of the cord until you turn the corner and start up one side. Now get the cord at the other end and go back across the bottom and start up the other side. Now move a few inches at a time on one side, the a few inches on the other. Keep on until you pull the cord all the way out. Enjoy your newly installed windshield!
It's actually easier than it sounds. If you're using Cal-Look seals and you don't have pop-out quarter windows, buy a whole set (windshield, quarter windows, and rear window). It'll set you back somewhere around $20. Replace the quarter window seals whether they need it or not. It's good practice for the windshield. The windshield is good practice for the rear window . . . it's the hardest one a bug 'cause it's got a pretty good curve to it.
