OK, the first one is quite easy.
Go into the event commands menu in common events, and get a conditional branch. Make the setting: when hero reaches X level then something happens. Go into the branch with when the hero becomes that level, and insert the command "Change hero graphic" and select the graphic you want to use.
IMPORTANT: select the battler to
the next command in this string should be "Change hero class". select what class you want to change to. remember, youll want some way to replace weapons to.
If thats confusing, ask somebody who can take screenshots. my RMXP broke T_T.