Preferably it 's best that both buyers and sellers agent be there at closing. But often the agent will end up just being window dressing at closing as the title closer / attorney is more than qualified to answer questions. Just make sure you are able to review the HUD1 with your agent, have your photo ID at closing and have the cashiers check for closing costs, etc. You may want to ask for the name of the title closer / attorney should questions come up prior to closing.
If your agent will be out of town, ask him/her to have one of his colleagues attend the walk-through and the closing with you. Even if you're represented by a real estate attorney, it's nice to have another person there on your side, with the file, who can get answers for you, if they should crop up.
I would never send a client of mine, especially a first-time buyer, to a closing without me, or someone I'd designated, to be with them.