If you are subpoenaed to testify before the grand jury, you must appear or the grand jury through the US Attorney can ask you be held in contempt and request a warrant be issued. Similarly, if the grand jury has already issued an indictment and the case is set for a trial for which you've been subpoenaed, you must appear or the US Attorney may request the judge issue a warrant.
There is always the possibility of plea bargaining for a lesser included charge. Also, you never know what a jury may do if you can get the judge to charge them on a lesser charge. So while you are correct that through complicity a get away driver is treated the same, this isn't always the practical outcome.
The possession of meth is a felony, so the sentence range is a year and a day up to 10 years if it is your first offense. The contraband charge is a misdemeanor, so it is punishable by up to a year. However, the reality is that if it is your first offense, you should be eligible for drug court/pretrial diversion/ or at a minimum, probation.
For a TOP I in Alabama, the rules of parole are as follows:
For a sentence of less than 15 years on which a defendant is recieving "Good time", the board of pardons and paroles will try to parole a defendant 12 to 24 months prior to their EOS date.
For a sentence of 15 years or more, a defendant generally comes up for parole consideration after serving 1/3 of their sentence or 10 years, whichever is less.
If you are "under indictment", that means you have been charged. You will either be arrested, or asked to turn yourself in to the United States Marshalls' Service. They will process you, and you will then appear before a United States Magistrate where you will be arraigned on your charges, and the Magistrate will decide whether or not to detain you until trial. In serious drug crimes such as a federal drug conspiracy, there is a presumption in favor of detention, so you would be well advised...
You can only be convicted of possession of a controlled substance if the State can prove beyond a reasonable doubt you either actually possessed them or constructively possessed them. This will be difficult if you haven't been there where the drugs were found in a year. You should have a court date with either Judge Lewis or Judge Ingram where you will be given the name of your court appointed attorney if you are indigent and cannot afford an attorney.
If your case has been forwarded to the grand jury, they will either "true bill" your case (indict you) or "no bill" it (dismiss it). Odds are they will indict you and you will be arraigned in Circuit Court. After that, a trial date will be set and you will be given a jury trial, unless you accept a plea. Best case scenario is the case is dismissed (unlikely). Worst case is life or 99 years (also unlikely).