Hi Paula
I'll be leaving Canberra late April via Sydney to the Camino walking mainly in May. I'll be 43 by then and walking on my own. I think some trepidation is perfectly natural and all part of the process. From what I've read here and in books it should be ok to walk and travel by yourself.
Having travelled a little over the last few years my advice would be to just be sensible about how you behave, be wary of thieves/ill doers - but don't let that hinder your enjoyment. Make sure you've left a photocopy of your passport and credit cards at home with someone you trust, that way if anything gets lost or stolen you know where the details are.
Remember not to pack anything sharp in your carry on bag as the security rules are very very strict now. Travel light.
Research your route but don't be tied down to a timetable. I plan to walk a few days of shorter kms (about 10-15km) then more as I get use to it, up to about 25 a day probably. Don't forget there is no shame in having to stop your journey or travel by bus or taxi for part of it - its all about the journey and what it means to you and what you get out of it.
I'm preparing now to get physically fit - I try to go to the gym a couple of times a week and do 30mins on the treadmill (about 3km) as well as general exercise. I am also walking outdoors most weekends, somewhere between 5-15km depending on weather/time etc - I am carrying my backpack (a Macpac Torlesse 35 litre - on sale at Paddy Palins at the moment) filled with about 7kg and wearing my new boots (Aku Ultralight, gortex) - so far so good, feels really comfortable and only getting a small blister on one of my heals.
Wish I could go tomorrow but alas I need to accrue more leave and save up $$$ !!
good luck with all your planning, excitement and trepidation - all part of the fun and the journey. Happy to chat about the anticipation of it all at any point.
cheers
Megan