B.D,
As you well know there are only two certainties in life...etc etc
My advice is simple, if you really want this then don't let anything hold you back. Get your Class 1 Medical first, strongly consider an assessment through GAPAN or one of the Integrated FTO's (do plenty of research first.) You will also have to strongly consider your family situation. You are moving from a securish (actually bomb disposal probably doesn't list under this section) job to what is a minefield (sorry) of whether you'll get a job after 50/60/70k worth of investment. If you do find an FTO that suits do your best to hit the books early..... Sadly the only person who can answer your question is you. Is 38 too old to start, in my opinion absolutely not.
You will get plenty of knock's 1) Aren't you too old 2) Top Gun jokes etc....
Give it everything, try your hardest and go for it....
TM