i would suggest taking two rigs. one filled with fresh 25# line and one filled with fresh 30# line. make sure your drags work and you know how to use them.
hooks and sinkers can be bought at the landing. they know what sizes are working at the time of your trip.
have the deckies double-check your drag settings and rigging. they want you to catch fish for them to gaff and filet. They make their wages on "tips for good service" and filetting your fish. 15% of the trip cost is traditional "tip". Filetting is $5-$10 depending on the boat and fish size.
after the boat "baits up", the skipper will have a safety meeting which will also included a projected intinerary and basic rigging instructions. if you have any questions at all, dont be shy to ask questions. chances are, others will have the same questions but dont want to speak up.
since this is your first trip ever fishing for tuna, dont worry about "fishing the slide", "throwing iron", or "swimbaits". simply change your bait often with fresh, lively ones and toss it back in at the "corner". Anchovies are, most often, the "meal of choice". Bypass the sardines if there are lively anchovies in the bait wells.
Re-tie your hook after EVERY FISH. Feel the top 10' of line for nicks, etc. Cut that part off, if it is damaged at all. Cut off five feet after each fish, anyway. Double check your drags throughout the day. Spritz your reels with fresh water at the end of the day and first thing in the morning...and double-check your drags again.
Since this is a two-day trip, BE UP AND READY TO FISH before the sun comes up. You will be drifting on the sea anchor all night. Bait fish will be gathered under the boat and unseen by tunas in the dark. As light approaches, their little silhouettes will appear as breakfast for any tuna in the neighborhood. Some of the best tuna bites are at this time..
good luck and enjoy your trip.