The Dayak's headhunting days are over, although there have been reports of a brief resurgence in 2001 including cannibalism during the clashes with the Madurese. However, it is unlikely that you will be served for dinner.
It is probably best to walk either with a guide or in a small party. You definitely should ask a Dayak to accompany you if you are planning to leave the main trails between the villages. Getting lost and spending the night alone in an unknown jungle would definitely be a memorable experience, but probably not a pleasant one.
Suspension bridges made of wood and ropes have the habit of swaying while you cross them. Some are old and in a state of disrepair. The Dayak know this and don't use them anymore. There are no signs to indicate their state, so if there's no-one around, you'll have to use your own judgment. If you doubt the bridge will be able to carry your weight chances are high that you weigh more than the wiry Dayak, look for a place where the river is not too deep and wade to the other side.
Log bridges can be very slippery. Don't lose your balance if you don't want to get wet.
talk
Indonesian is generally understood by the village chiefs and the younger people. Knowing a few words in the Kenyah language helps a lot.
See also: Kenyah phrasebook