Well, that is an amazing endeavor! As for the windows, easy , just use isomalt or sugar. For trees you could go with pretzle sticks and royal icing limbs, several stages for drying time.
I don't remember where I saw it (but I know it was on tv) but someone covered grape stems with melted chocolate and let it harden. You could try that then using a leaf tip to make the leaves on it. Good luck with the cake.
I used gelatin sheets for the windows on my house cake (see my photos) - they work great! I also tried the grape leaves dipped in chocolate - worked well. I used the wilton green candy melts. For the trunk, I used gumpaste over a lollipop stick and painted on milk chocolate candy melts. The tree looked a bit more diorama like but that was the look I was going for (see my tank cake photo)