I think it's better for you to try it first at the nearest Nokia Center.
p/s: Just to let you know that there's still no whatsapp yet. So make sure to study the apps available first before you buy N9 
http://n9-apps.com/
http://store.ovi.com/

Very easy.

The thing is... no matter how complicated or hard, you only need to learn ONCE. It's always hard (especially when you switch) when you use SOMETHING NEW, no matter how simple it is.
Let's say you bought a new Digital Camera, surely you see the menu and so on, you wanna "pengsan" like very complicated, but after you "play-around", actually, you will slowly find, it's very simple, heck you may even feel lacking this and that, why got no this option, why got no that option (but when you first touch it, you feel like soo many things).

Even Android maybe complicated and have many features/settings/etc. Once you get used to it, you will feel still feel that, it's incomplete and missing this missing that. But having more things/features, you get to enjoy more.

As for N9 (MeeGo), it's like between iOS and Android, it's simple like iOS(easy to use, little/no customization, etc), yet powerful like Android (little/no restrictions, no need to worry sit in jail, etc), although actually, there is one primary advantage of MeeGo over the rest, the true multi-tasking.....
This is OS wise... which most people don't really bother because most people actually want/bother about apps/games only. So, really depends what is important to you.

Whether 16GB is sufficient or not depends on how much music you have. This is the main thing to consider as you will normally leave all your mp3 files in the phone. Other files like video and photos can be deleted after viewing. The 16GB N9 will give you 9GB storage. The apps you install will not take up this space. If you are not sure it is better to go for 64GB as memory is fixed (no micro-sd card) and the extra cost is less than RM300.

16GB should be kinda sufficient as you will have 8GB for your personal data (music/video/photos/documents/ebooks DLL). For emulator games, you may want to check emumaster <http://store.ovi.com/content/207988> and you will need to have the ROMs stored in certain location as instructed to play.

There will be no external storage in terms of micro sd/mmc etc., however PR1.2 will probably come with Dropbox support (btw, there's a dropbox app in the store) and will be released soon (Developers are currently beta-testing it) and it should provide you another option to manage your content.

as long as the answer do not violate forum rules, i am sure there will be someone answering it for you

you may probably want to ask android ppl, maemo/meego don't need rooting to get things done to certain extend (aegis comes in mind, but that's a different topic)