The student has already done both things that cause his damage his case the most. He's flown through the restricted area, and he contacted the FAA without consulting an attorney.

The FAA can have a difficult time placing the pilot in the cockpit; usually the evidence is given by the pilot himself when he or (or she) contacts the FAA. It's for this reason that contact should not be made until first speaking with an attorney who handles FAA matters.

Tell your friend to sign up with AOPA immediately and buy the legal plan. It may not cover him in representation at the appeal, but he will be able to get consultation. Don't do anything further until consulting an attorney.

Wil this impact an airline career? Maybe, maybe not. Early in his flying, probably not a major impact, but take it very seriously none the less.