Hamill was disfigured in a car crash immedeately after the reviews came in for Star Wars. He had signed on for a season of the yet-to-be-filmed pilot of "Eight is Enough" for TV, which would prevent him from making the sequel due to his NBC contract. He was driving his BMW on a bad highway at night
in the rain when he came to a very bad turn and didn't swerve in time. He smashed through the shoulder and the rail and went about 30 feet into a ditch at 40 mph.
He had to get reconstructive surgery, and was in the hospital for, I believe, two months. He was also clinicly
depressed and had to be treated. Luckily, he didn't have to join the cast of "Eight is Enough" since his hospital stay overlapped principal shooting.
The opening of ESB was made to accomodate his facial change from the accident.
As for Hamill doing voice work, he's been doing that since before Star Wars, on a 70s eco-minded fantasy called Wizards (back in 1976, though he was labeled has "Mark Hamil" with one L)
He's done voice over work for years. It's easy, not as taxing as stage or screen and it makes decent money. I talked to Bob Bergen on occasion, who is not only in Atlantis along with Hamill, but also did the voice of Luke Skywalker in numerous Lucasarts games. Bob makes a nice amount of cash for his lowly job. Imagine how much Hamill makes!
Hamill is getting on in his years. He's not an exceptional actor, but he is very much underrated. His work in movies like "Slipstream" (1989) and The Flash TV show, where he was the Trickster. He's also penned a script in the past 3 years called "The Black Pearl" which he's having problems being made since he wants to
direct it. He's also making a large appearance in "Jay and Silent Bob Strike Back", of course appearing as himself.
This information was brought to you by a 3 year member of the International Mark Hamill Fan Club memeber.