Legal aid provided free legal help to people seeking SSI, many states pay Legal Services to represent you in your request for SSI. Generally they know SSI disability law better then most people and will do a good job representing you in your quest for SSI.
Do NOT wait to see the Legal Aid Attorney, file the appeal with SSA as soon as possible. When it comes to the reason why you want to hearing just write down you are still disabled. Legal Services may have trouble getting you in within the 60 day appeal period so do NOT wait to file the appeal till you see the Legal Aid Attorney.
At the hearing, there may be an Vocational Expert will be present (In almost all ALJ hearings regarding adults in the Pennsylvania that is the case, I do not know what they do in your home state even through SSI is a Federal Program, the rules regarding SSI do vary depending on what the Federal Court of Appeals that covers your state has ruled on what is required in a SSI hearing).
Legal services can NOT handle your mal-practice suit, you have to go with a private attorney for that.
In my experience, when it comes to past relevant work like your past job as a waiter, an ALJ will ask questions of the Vocational Expert in the hearing. Your lawyer should listen to the questions (and most will) and if the right questions are not asked, asked the questions themselves.
Now you did NOT mention your age, age is an important issue under SSI disability. If you are below age 50, you must show you can NOT do Sedentary work, which is work that requires you to be on your feet no more then two hours a day (Through this can be in 10-15 minutes intervals) and lift no more then 10 pounds. Further more the Vocational Expert will testify that you have to be able to perform within 90% of the average worker, work for two hours take a 15 minute break, work another two hours, take a 30 minute lunch break, work two hours and take an 15 minute afternoon break, then work two hours and go home. If you can NOT do that level of work (And that has to be decided by the ALJ not the Vocational Expert) you are unemployable.
Other things that make you unemployable is missing work do to your problems more the two days a month (Which can include the days you miss work do to having to go see a Doctor or other medical provider) or miss work more then one day a month every month for some other MEDICAL reason (i.e. NOT wanting to work is NOT enough, you must show it is do to Medical Reasons). Now, Psychological factors can be Medical Reasons, i.e. you do not want to go to work but the reason you do not want to go to work is not laziness but some psychological reasons, then that also precludes from working and thus you are disabled for SSI purposes.
Notice, the key is the testimony of the Vocational Expert based on what the Medical providers say your restrictions are. SSA does NOT believe your Doctor has the training to determine whether you can work or not (The Vocational Experts have PhD in work related fields and thus in the best position to say what a person with your medical restrictions can do in the terms of Jobs that exist in substantial numbers in the National Economy). Now the Vocational Experts will NOT testify what you can do, but only someone with your education, work background and restrictions as set by Medical Providers (and if the providers disagree then it is up to the ALJ which medical provider to go with) can do. It does not sound like much of a difference but all the Vocational Expert is testifying to is the question put to him by the ALJ or your lawyer, so listen to the question being asked.
Now, my experience has been when an issue involved what jobs you can do, the case almost always go to an ALJ whose decision will be based on what your Medical providers say your restrictions are what the Vocation Expert testify what a person with those restrictions can do when in comes to Jobs that exist in substantial numbers in the National Economy. Thus file the appeal for an ALJ hearing, that is the best place to get awarded SSI benefits for a person with your restrictions.
Here is a paper where I simplify the Social Security Disability Test. Read it for your education as to what is being disabled is for SSA.
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=250x353#376