>What's the best way to plan a "big" trip
>without being overwhelmed by the details of the trip?

1) Don't sweat the small stuff: Know that, wherever you go, someone will have found a better / cheaper hotel, or will have paid less for a taxi fare, or has a better tour guide. Don't worry about it - Just enjoy where you are.

2) Buy and read, and re-read the guide books. I'm personally a big fan of the Rough Guide books - I find them a little more "well-rounded" than the Lonely Planet books. Or even better, read both.

3) Start making your list of things you want to take today. Keep refining the list, refining and refining. For me, travelling is all about good lists.