I don't, but I want to get one for my husband for his birthday. If I get the dock, can 2 people play the same game of it's on a TV or do I need 2 decks?

No, you don't need two decks. You need:

• Steam Deck
• USB-C Dock with power delivery (for example, the official dock)
• 1 to 4 game controller (most bluetooth controllers will work fine)

However, there are not very many "Couch Multiplayer" games on steam. Most multiplayer games are online.