I have had a few of the exact fixtures you describe. No, nothing will
explode. It will be fine.
To save a few pennys on electricity cost you can use a compact
florecent rated for outdoor use, to get longer life of the bulb you can
use a bulb rated 130v.
Seems you have a 60w bulb already, just install it and be done with it.
When the buld burns out just replace it with what you have on hand or
get something different. No big deal. The fixture probably says 60W max
and UL listed, just do not use higher than what its rated for and you
will be fine.