the same applies to nn dmt it needs maoi to make it orally active. dmt smoke isnt that harmful i feel bad effects from vaping other things on my lungs depending how much i do but dmt doesnt appear to have any negative effects, it also helps that i tend to do one or maybe 2 pipes only with dmt, where as other things il do more. as long as you dont burn the dmt and it all vapourizes it shouldnt do much harm not unless your smoking it like a crack'ead.
personally id try smoking/vaping it first either in changa or freebase in a pipe which freebase would be healthier, then if you want a longer experience try it orally. up to you but i know oral dmt is not something id go straight into trying first, as you dont know how the dmt will react with you an make you trip. if its bad orally is gonna last hours but you may be able to work on it, where as smoked will be over in 10 mins probably less.
you can always smoke more dmt if its really good or not strong enough, you cant take it away if done orally if you have a bad trip or you just dont like it, your forced to ride it out. i suppose you could just take small doses an top yaself but thats easier an safer with smoking/vaping it.