Almost certainly. If you can run for 10 mins, you can learn to run for 30. If you can 5K, you can 10k, half marathon, marathon - just takes time. You've done the hard bit though
Build up slow
Book an event but give yourself an escape route - don't spend the money if you can't afford to pull out - don't force yourself to keep training when injured.
5 to 10% - calculator?