If you're obviously not Japanese, nobody will expect you to speak any words of the language at all. If you look like you're from an English-speaking country, in fact, a lot of people will use that as an opportunity to practice their English.
That said, if you know a few basic words of politeness, people will think better of you than someone who can't even manage "please" or "thank you". Learning a few counting words can be useful if you plan to go shopping, too.
Most places in Tokyo will have Western-style toilets and Japanese-style toilets. You want to use the Western-style toilets. Really. You do.
Eat stall food whenever you can. Tokyo's street foods are amazing and you can find stalls potentially anywhere, but especially around train stations.