You don't have to wire up the power on digital IC's. The Power pin are hidden and the only thing you have to do is place VCC,VDD, VSS or DGND on the schematic and the IC's will be automaticlly hooked to them in the background (you won't see any physical connections).
For the second question. The only way I know of to do this is to edit the components symbol in the Symbol Editor. Double click on the component and goto the Value tab and you will se where it sys to "Edit Component in Database" Click that and it will take you to a new dialog box. Select the tab "SYMBOL" then you will see down below where it say "EDIT" From here you will enter the symbol editor and can edit the component symbol however you like.
I would suggest reading the Multisim Manual about the symbol editor to familiarize yourself on its operation. I don't use it that much and would have to review this myself.
I hope I have helped.
