replace broken Anderson S-400n DH Tilt wash assist?

Thanks for reaching out to us! I won't lie, installing this part can be very difficult. 

As for reinstalling, you have to compress its sides with your fingers and put it in pointed end first. You have to roll it in the same as you rolled the old one out.

It may sound easy on paper but it is a pain in the neck. If you really have a hard time with it, you may want the help of a local professional who has worked on Andersen windows like this before.

I'm afraid we don't have a video for this particular part. You are not alone, though; this is probably my least favorite part to install. The instructions provided above are the official Andersen process, and indeed it is the only way I know of, but it makes it sound way easier than it actually is. It's VERY difficult, and in my opinion not the best design. As Emily mentioned above, if you're unable to do it I would suggest having an Andersen dealer send someone to your house to do the project for you.