Slightly complicated HD + OS upgrade

I have a macbook pro 13" mid 2009, so I currently have Leopard 10.5.8 OS and an internal HD of 150gb.

What I would LIKE to do (by myself and not let someone do it for me):
Upgrade my HD to a 500gb Seagate HD 7200rpm, which I bought. The physical task of doing it should be easy.

Where my question stems from:
My end goal is to have the new hd and partition it with Lion OS and Windows 7.
I currently have the windows 7 disk, didn't get lion yet.

I'm not sure the order I want to do things, and this is where I need help.
I could upgrade to snow leopard on this computer(but i'd also have to get snow leopard), then go to lion, then use superduper to clone that hd and then install the new hd and put the clone on it.
OR I could use my external/portable HD (320gb seagate) with a firewire 800 cable to back up everything on my hard drive now (applications, documents, settings, etc.) then just put the new hd in, load lion as a clean install, and then put my stuff from the external on (but i'm afraid i may lose data or settings).

Basically, I want to do it myself but I need suggestions, I don't want it to be complicated. What is the best way to get my end goal, and why? Why not go another route?

So, if i do that, i would not need to bother with purchasing snow leopard, i can just get lion and put in on a new drive.

And when i do that, i can partition the drive while i am loading lion (right?)
and leave my space open for windows. then migrate everything over from my back up, and then put windows on the other partition.

BUT:
what kind of back up should i do? /what method should i do?

i know i can use migration assistant but i'm not sure how to back up my applications and settings onto my HD,

OR if i should use super duper?

I'm not sure how i should do the back up.