Miles,

Yes, there are plenty of tours. A couple of notes:

1) You will need a travel visa if you do not have one (or a passport from exempted foreign countries). It can take a minimum from 5-10 business days to get. I think it will be a couple hundred dollars ($100 visa fee + $130 processing fee). I've been through this process twice already and its a pain.

2) You will also want a Yellow Fever vaccine if in the Amazon, it is required for getting into other foreign countries afterwards.

After you get down there, there are plenty of tours and options. I'd recommend checking out TAM. The big airline down there has all kinds of services.