nice to hear from you. If you look at the Auenzeitung on page 12 (p. 7 in the PDF file), you'll see an article about the grave being renewed in 2010 (among others), with a photo on p. 13 (the facing page on the right). I work with a similar group where I am, trying to preserve old graves. It's interesting and also a kind of sisyphus Arbeit.
There are also articles about Iffland's grave on Iffland Schauspieler and Wikipedia, but maybe you've seen those and there are no details about the renovation(s). I made a memorial for the grave of August Iffland's brother Christian in Hannover and Frank K. nicely linked them.