Questions about how Grand Prixs operate
At a Grand Prix, all the same tasks exist as on a small local event, but on a much larger scale. Rather than having to put up a couple of sheets of paper so that people can find their table for a round, for example, you are likely to have split the pairings into 6 name ranges with 2-4 sheets of paper in each and to stick two copies of each range around the venue in order to avoid the pairings board being such a crush. As a result, judges work in teams in order to get tasks completed efficiently, and being able to have a sufficient grasp of the logistics of a large tournament in order to be able to be in the right place at the right time is massive.
You'll be glad to know that there isn't generally a judge stuck counting match results - result slips are distributed to player tables by the papers teams early in the round, and players (and judges) bring the paper slips back to the scorekeeper when matches are done. The scorekeeper enters results into DCIR as they come in and, with the exception of judges helping to sort slips late in the round at a large GP (so that we can find them again if there are problems), the only judge involvement in monitoring tables comes right at the end of the round, when the scorekeeper provides a judge responsible for coordinating end of round procedure with a list of tables which are still outstanding.
Judges very rarely fill one role for the entire tournament, unless this is fulfilling a specific request either from themselves or from the TO to the head judge. You'll normally be on a different team each day, and every team has a whole range of tasks which you will be expected to help out with.
As Chris says, in most events it is unusual for a level 1 to be on the Grand Prix main event - because level 1 judges have no requirement to know the IPG, we avoid putting them as floor judges on high-profile Competitive REL events such as Grand Prix where possible. Side event tasks are hugely varied and can often be more important to the Tournament Organiser and more logistically demanding, especially if you end up involved with on demand events in happy hour! It's often more interesting than the main event as a result!