The literal, physical coming of Christ is a fundamental of the faith. The entire evangelical movement, which later split into fundamentalism and New Evangelicalism, held to the fundamentals of the faith. There were a couple of different lists, but they always had the literal, physical coming of Christ. The famous series of books called "The Fundamentals" had three essays that taught this. So yes, full preterism is a denial of a fundamental of the faith. It is also a huge error in Christology; John taught that teachers who erred in Christology were to be avoided (2 John 9-11).
It's very simple to disprove the full preterist idea that the coming of Christ in AD 70 was only spiritual. Thus, it if that coming was not physical, then Christ has not really come yet. asterisktom and I use to tangle on this point, and when I used the Greek to disprove this so-called spiritual coming, he told me I relied too much on the Greek. Funny, I always thought that the NT was written in Greek. Don't know how Tom decided the Greek was not important.
Anyway, rather than belabor the point, I'll simply make one point from the Greek, though I have made many others in the past here on the BB. The word Greek parousia (παρουσία) is used in 24 verses of the NT. It always--ALWAYS--means a physical coming or presence. For examples, see 1 Cor. 15:23, 16:17, 2 Cor. 7:6-7 (twice), Phil. 1:26 & 2:12, etc. It occurs four times in Matt. 24 alone to refer to the 2nd Coming of Christ, but also in 1 Thess. 2:19, 3:13, 4:15, and many other times. Therefore the 2nd Coming of Christ is still future and still physical, since the preterist admits that Christ did not come physically in AD 70.
P. S. asterisktom believes that Christ no longer has a physical body--that somehow the Incarnation has been reversed, though he doesn't say how that stupendous event happened. So when Christ "came" in AD 70 He just came as a spirit. And by the way, "spiritual" in the Bible does not refer to being "a spirit" but speaks of things of and pertaining to the spirit. Where did Christ leave His wonderful resurrection body? Preterists don't know! But "the body without the spirit is dead" (James 2:26). So somewhere in Heaven, perhaps, the dead body of Christ is enshrined like that of Lenin in Moscow? Naw.