I think your approach to go down and feel it out is a wise one.
I went down with a long retreat booked and ended up leaving early to feel out Iquitos and some other spots to drink at during my month there. Go for longer if you can afford it. Gives you time to adjust to the country and jungle.
There are alot of tricks to living and seeking good shamanic experiences in and around Iquitos.[I don't know about ceremonies in other areas (Cuzco, Pucallpa, almost anywhere in Peru has some) but Iquitos and the jungle surrounding it put off a great wild west city surrounded by boundless untamed jungle vibe.]
Since I couldn't remember them all, it being a year since I've been back, I can only point you in the direction of some folks down there who won't steer you wrong. These guys know about most places to drink in the area and will steer you clear of people who will waste your time or rob you etc. They also run a really cheap hostel with real positive vibes and people from all over the world. The owners mostly speak English and Spanish but all kinds of people come through to stay there. The people there were some great and real characters and helped me and my partner alot when we were trying to make our way around and outside Iquitos. They have a few of their own secrets to share with medicine seekers also.
Its a good place to start your journey and its right in the main square of Iquitos 1 block from the Boardwalk on the Amazon.
I believe their e-mail is available on the web
La Casa Chacruna
Iquitos, Peru
PM me any more specific questions
In the province of the mind what one believes to be true, either is true or becomes true within certain limits. These limits are to be found experimentally and experientially. When so found these limits turn out to be further beliefs to be transcended. In the province of the mind there are no limits. However, in the province of the body there are definite limits not to be transcended.-J.C. Lilly
The Spice must flow
Zat was Zen and dis is Dao.