Excellent. The definition of gospel you found on lds.org is a good place to start. It identifies the Atonement of Jesus Christ as "the central doctrine of the gospel." The same glossary defines atone as follows:
As used in the scriptures, to atone is to suffer the penalty for sins, thereby removing the effects of sin from the repentant sinner and allowing him or her to be reconciled to God. Jesus Christ was the only one capable of carrying out the Atonement for all mankind. Because of His Atonement, all people will be resurrected, and those who obey His gospel will receive the gift of eternal life with God.
Note that these definitions make no reference to the many distinctive doctrines and practices of Mormonism that the original article mentions: eternal marriage, temple work, the Word of Wisdom, and so forth.
I admit that many Mormons use gospel as a synonym for all of Mormonism; but such usage is imprecise. As used in the Book of Mormon, the gospel is the "good news'' of Jesus Christ: He atoned for the sins of the world; He arose from the dead on the third day; and He has provided the means whereby we may be cleansed from our sins and enter into the kingdom of God. (See 3 Nephi 27:13-21)
And that is typical Mormon misdirection and double-speak since we have spent months posting what your religion asserts are/is 'the gospel' to be obeyed to obtain salvation/eternal life with God. Mormonism has as fundamental to this supposed 'gospel to be obeyed' all the things you deviously inferred were not a part of the definition of 'Mormon' gospel for salvation: temple recommend, Mormon baptism, eternal marriage, etc ... or should we use Smith's 'and so forth'(?). How very devious that
How about answering a question, truthfully, without cunningly devised phrasing: do you believe you receive eternal life by the presence of the Holy Spirit in you ‘after all that you can do’? ... And even that question is hard to ask of a Mormon since you people claim the Holy Spirit is a separate being from God the Father Almighty and Jesus Christ!