I am thinking of cancelling my guide for Istanbul---main question is: tips for the Grand Bazaar since I hear it is endless and wonder if there are certain areas not to be missed (and perhaps not to use a guide for this)

While a guide will take you to some of the more unique shops, I think the Grand Bazaar can be enjoyable explored on your own.

wordsmith, I'm not sure I completely understand your question, but I would keep my Istanbul guide. I don't think you would need to use him/her while you are browsing the Grand Bazaar. You are not obligated to have him/her guide you through the bazaar. You might consider his/her "tips" on certain stores, but you are not obligated to visit or purchse from them.

No need for a guide in Istanbul. Plus, if you go to the Grand Bazaar (or any other shops) with a guide, the prices you pay will be jacked up by the guide's commission.

No need for a guide in the Grand Bazaar. This is where you want to wander and wonder. Haggle, haggle, haggle. Avoid the guys out in front.

Much more fun finding your own way around the Grand Bazaar. In fact I agree that goes for Istanbul as a whole. All you need is a guide book to give you a rough idea, a map, and a sense of adventure. Take a ferry across to the other side - use the trams to get to places like Kariye Camii.

Cheers.

Cancel the guide. i really, really like Istanbul, and getting lost is the Grand Bazar is FUN. You always find your way out.

A guide is not just unnecessary in Istanbul, and in the Kapalı Çarşı in particular, it's even a really bad idea. I bet 99 out of 100 guides would guide you to shops where they're getting a percentage of what you buy - and those are not necessarily the best or the most interesting shops. This is Turkey's most typical way of making more money from tourists than they would normally have to spend - cause it goes without saying that the guide's percentage is being paid by nobody else than you, in addition to the tourist price that is (in shops prone to this kind of agreements) already more than double of the real price. It's far better to browse the city on your own, and find those trustful and honest shops that don't have tourist prices at all...