Booking a long flight. Should I use a travel agent?

I am looking for advice.
When my DH was alive, we planned our trips together and enjoyed doing it. Now as I fill in dates and times on the airline websites, I'm filled with dread.
Partly because I am afraid I'll get it wrong but also fear of the actual journey. It will be the first time I have flown alone for many years . I very much want to visit my DS and his family in NZ.