Now, I'm a bit suspicius of guides sometimes as it can be really expensive, and being a canny Scot, why spend money you don't have to! But on one of my visits to the Kremlin, with my mother who wanted (and paid for) a guide, I succumbed. There are lots of them, they hang around outside the entrance, so even if you're not with an offical party, you'll find one. Don't be afraid to haggle over price. The lady we got was absolutely fantastic, great English, knew her stuff, and I was so glad we'd hired her.
We went to the armoury, which is so much more than that! The old dresses are fantastic - and the Faberge eggs - the only place we saw them. The armour was good too, great for the boys!
The Kremlin, for beign the seat of government looks very like a museum - for one very good reason. Many of the government buildings are underground. As you come in, look in the glass fronted building to your right, and you'll see lots of escaltors going down into the earth. This is because, under Communism, it was not permitted to build any higher than the Cathedrals in the Kremlin (bizarre given the lack of respect for God, but true all the same).
Another interesting fact, this time not from the guide, is that the Red stars on the towers are lit all the time. They have only been switched off once in recent history when a famous Russian film director, Nikita Mikhalkov, was making an historical drama about pre-revolutionery Russia, the bright red stars would have been out of place. Other film directors dream about having the power to get something like that done, but no-one else could!
The Kremlin can work out very expensive if you go and see everything as you have to pay separately for entry to different buildings, like the Cathderals, Armoury, and so on. But your entry ticket lets you wander around and see the Tsar Cannon and the Tsar bell, named for their size. The Tsar bell was broken before it ever rang, kind of a waste, but what can you do! The Cathderals are beautiful outside, but I didn't go in, so can't tell about them inside! There are lovely gardens, and a great view of the river - over to the British Embassy where they used to lie on the roof to spy on the Kremlin - and Red Square, not to mention the rest of Moscow.