I've been to Japan twice; first in October 2004, then again this past November. I'm going back in May (my girlfriend lives in Nagahama).
I'm 6'2" and the shower heads were a bit difficult to navigate around. The bathrooms in the hotels tend to be eentsy on the whole. You should try the Japanese-style baths that a lot of hotels have. The experience is a lot more pleasant than trying to wedge yourself underneath a shower head that's located somewhere just below your neck.
I was very impressed with Japan the first time I went there. I was with my girlfriend most of the time, so I had someone with me who knew the language and the culture. We stayed one night at an old house (built in 1920) in
Kyoto; the rest of the time was at hotels in Tokyo and Nagahama. This last time I was there I had picked up some more of the language, so I was able to get around and order food more easily on my own (which was good since she had to work a few days while I was there).
The first time I went she took me to a lot of temples and castles, since I'd told her that was what I was especially interested in seeing. In Tokyo we went to the Edo-Tokyo Outdoor Architectural Museum, the Imperial Palace, a
sumo school, Asakusa Temple, and a few other places like that. Oh, we also went to the Pokemon store. I'm not a huge Pokemon fan, but it was certainly interesting.
The language barrier depends on whom you're talking to. My experience has been that most older people don't understand a lot of English, while most younger people have had at least a couple of years of high school English. This isn't a hard and fast rule, though, so there are certainly exceptions.
A lot of restaurants have menus with pictures of the food that you can point to. You'll probably won't starve to death.
Have fun!