Spend 6 hours:
package live site, clone to local development environment
disable local contributed modules
turn on maintenance mode
upgrade local core to Drupal 7.x version
Convert custom theme to D7
upgrade contributed modules
configure contributed modules
use 7.x version of cck, use content migrate module to migrate fields to 7.x core
package local
backup live site
transfer local to live
DONE!

There should not be any difference from visitor point of view
I am also confused after live is being transferred:
"huh? finished? they just looked exactly the same"
until I opened the admin pages and saw Drupal7's seven theme

The next steps will be turning on the multi-lingual options
converting this blog from mainly chinese to bi-lingual
2013 GoGoGo!