Where is the potion shop near the second dungeon

Yes, the original Zelda is available on Nintendo's Virtual Console. I believe the majority of the NES games are 500 Wii points.

To obtain any Virtual Console games, open the Wii Shop Channel and choose the Virtual Console icon. You can browse the games by system or genre. Once purchased, the game is downloaded to your Wii and appears in one of the channel screens. For NES games, you can get away with using the Wii remote turned sideways as your controller, since you only need two buttons. For SNES and up, you will want a Classic Controller, since that gives you all the buttons you need.

Commonly with virtual console games, you can hit the center button (Wii menu?), and exit the game. This will automatically save the state of the game. Next time the game loads you'll begin at that spot; however, after reloading once the save state is no longer available -- resetting the system won't allow you to resume from that state again.