15.1 The word for Gospel/Good News is euangelion, coming from eu for Good and angelion, the word for message (like Angel=messenger). Interestingly, Paul uses this as a verb as in "the good news which I good newsed you with." We could write in English, "The Gospel that I evangelized you with," but in Greek they are the same root word
15.2 Save (sooz-oo) is a present passive here -- salvation is an on-going and passive activity for Paul.
Also, in this sentence, the word for "if" is "ei," which can be translated since when the verb it is connected with is in the indicative and not subjunctive mood. This, this sentence could read, you are being saved, since you hold to a word which I proclaimed to you. Unless of course, you believed in vain.
Also, the word "the" is not used with "word (logos), but rather "tini" is, which means, "a" or "certain" or "some."
15.3 This is not a Greek note, but a more theological one. Paul's primary category of thinking is not simply sin...but here it is, the big deal is dying on behalf of our sins. Fascinating.
15.8 The word for "untimely birth" (ektrooma) means stillborn or even aborted.