Intermittent Service Battery Warning

Hello all,

I keep getting the "Service Battery" warning intermittently. If I restart when the computer is plugged in, it disappears, and it shows again when using the battery extensively, for instance, when in travel.

The cycle counts marks 287. I have an appointment for the Apple Store tomorrow, but I am panicking because I need to travel the next week and I absolutely need to take the computer with me. I will need in addition to this to buy an external hard disc.

What do you think is wrong? Will they service the battery? How many days they will keep my computer? Can I wait until I am back from my travel (that is in 5 weeks) to take it to repair or it could be some issue?

Thanks for reading.