Oh I am DEFINITELY going.
If I absolutely had to change into something, I would like to be a griffon so I could keep using hands and still eat meat. even if it is just fish.
To be completely realistic, the first thing I would do is find a place to hide so I can think about how exactly I'm going to go about my interactions with the locals, and count my bits.
I don't think that I would be all gung ho and visit the mane six straight away. I would probably ease my way into the community a few ponies at a time. Because lets face it, its a big new place with (although familiar) strange beings.
In regard to how long I would be staying. Forever. If my friends and family knew that I was adventuring in another world, they would understand. After all they all taught me that when you have a once in a life time opportunity, you do not pass it up.