You have my sympathy! We normally try to go with tour Cos for complex itineraries - Wendy Wu for Asia, Riviera for Europe, etc etc.
However, our 8 week trip of Aus n NZ was all internet researched/booked.
What could possibly go wrong?
Being retired gives me time to do the research, a paper-based timeline highlighted what I needed to do, and a simple filing system on the pc seemed to work. (Paper for the timeline - so I could see all the issues at once)
At least everyone involved spoke a sort of English!
Fortunately, it all worked. Other than booking a 5 star hotel in Auckland in error!!
Virgin Aus did their best to foul it up - they sent my bags to Hobart instead of Cairns, and then lied and lied and lied.
Otherwise, fine!