my ground glass screen appears dull, and dirty. what is good to clean it with, which is not harsh and will not scratch the screen? is lemon juice ok?

Hi.
This last summer there was a posting in this forum "Cleaning and lubricating my 'New' Crown Graphic" that you may wish to check out. For your information, there is a search function in this site to aid users in finding the information that they want. Also, simply browsing and reading the articles on this site as well as the postings in this help forum will reveal much useful information.
Dave

I've used Windex® with success. If you want to be ultra-safe, rinse it with distilled water afterwards, or use distilled water in place of the Windex®. Pat dry with a lint-free cloth, such as a linen pocket handkerchief; don't use anything paper or you'll be seeing little specks forever. Using distilled water, whether alone or as a final rinse, will guarantee that the glass dries without spotting.

very good advice. distilled water and glass cleaner it is.

the focusing screen is not usable, though i tried to clean it. it has scratches on it, affecting focusing. what would be a new suitable replacement?

http://graflex.org/helpboard/viewtopic.php?t=5208&highlight=ground+glass+replacement

Boy, the search function here works well.