Here we have another example of a Hebraism in the text: namely, the use of and between a preceding subordinate clause and a following main clause. Such a construction is not English, and as a consequence Oliver Cowdery omitted the and when he copied the text from 𝓞 into 𝓟. While copying, he also replaced the modal shall with should, undoubtedly under the influence of the occurrences of should found just before and after this clause. The use of the original shall is, of course, more vivid.
Hebraisms like this (when supported by the earliest textual sources) will be restored in the critical text, even though they are not easy for English readers to understand. Note, however, that the following sentence (“and if I should say it / it would be done”) also involves an if-clause, but in this case there is no and separating it from its following main clause. In other words, the original text varies with respect to this Hebraistic construction. For a complete list of where this Hebraism is found in the earliest textual sources, see under hebraisms in volume 3.
Summary: Restore in 1 Nephi 17:50 the original Hebraistic and that connects the preceding if-clause with its following main clause; also restore the original modal shall.