Just work slowly and you'll do fine. Don't remove too much at any one time.
I know that replacement sprues can be gotten in the U.S. from Tamiya, but am unsure of the availablility in other countries.
If all else fails, and you really botch it up, you can try adding some thin plastic card to patch the area or in an extreme case, cover it with a tarp.
Happy Modelling and God Bless
Robert