i'm wondering if its possible to attach several images to a post then display those images in a thumbnail/fading gallery?
By the way, the images should also be resized to a fixed size + thumbnail.
Yes, you can use the standard wordpress [gallery] shortcode, after having attacched the images to your post.
To attach images to your post, you can use the button "Upload Media".
Upload the image from your disk and the press "Save Changes". The image will be attached to your post.
Then use the gallery shortcode to insert the gallery in your post.