For first time visitors, the second floor will help people understand the history of cup noodle development and production. But the real fun happens on the third and fourth floors.
I spent most of my time at the museum in the Bazaar. The dishes are half-sized, and I hadn't eaten all day, so I easily downed two orders of noodles and one order of the custom mini-dish noodles.
I saw that they have a few noodle dishes that aren't soup - spaghetti was one of them. I would like to return and try the other noodles sometime. I saw they have a set offer that provides a discount, though I don't know the details. Each regular size bowl (half-size as compared to a regular ramen bowl) is 300 yen. Each country also has a local dessert (300 yen each) and a local drink (200 yen each) - a free-refill drink bar is 200 yen.
There's a gift shop with plenty of cool souvenirs and a little bit of overpriced instant ramen. Prices on the souvenirs are generally reasonable (for Japan), too!
Admission to the museum is 500 yen, but keep in mind that it's not worth visiting unless you pay extra for the experiences and/or food. The Cup Noodles Museum is open 10:00-18:00 (last admission 17:00), closed Tuesdays.
Access is a little bit tricky at first. It's best to arrive at Minatomirai Station on the Minatomirai Line (an extension of the Tokyu Toyoko Line from Tokyo). Follow the signs to Yokohama Cosmoworld (the station has several exits and it's a maze!) and then head toward the Ferris wheel.
You'll cross a bridge as you approach the Ferris wheel; continue following that street to the stop light, and you'll see the museum building on the opposite corner. Refer to the photo at the top of this post.