If my MacBook came with a 60W MagSafe 2 charger, will a 85W MagSafe 2 charger work for it and be safe to use?
Yes it will be fine. Apple made sure you can't mess anything up. Some larger mac-books need the high wattage, but if yours does not need the extra wattage it will still work. The power adapters automatically provide the wattage required up to the maximum.
check voltage supplied and polarity of the voltage. plus, does the plug fit in?
As long as the output voltage is the same, it will be fine. The computer will only draw the current it needs.