You can use Expresssion to edit and maintain Dreamweaver created sites but Expression only understand Dreamweaver 4 templates not those of later versions.
There is no need to "import" any site into Expression Web simply point it to the location of your local copy of your Quark site. If you do not have a local copy then create a new empty website then connect to your web host via FTP and publish it down.
Note, I do not know what sort of websites Quark creates and many desktop publishing programs do not create standards based sites so the results may not be compatible with curent coding practices. Whatever you do I would recommend that you archive a copy of its current state before you begin any editing.
Cheryl D Wise MS MVP Expression Instructor: starttoweb.com