Thanks for the question.
Sometimes we can find good advice coming from non-Catholic sources so that is not a problem. However, you must be careful not to confuse doctrinal points that may contradict Catholic teaching.
If, for example, the Protestant preacher convinces you that you need not worry because "once saved always saved," that is heresy. (There is a lot more nuance than that.)
Salvation is an important area to understand in terms of Catholic/Protestant differences.
We hold to "moral assurance", vs. "total assurance". While I don't want to get too far into the particulars here, suffice it to say that you must know your faith and its doctrine well in order not to be confused or led astray by other denominations. The only chance for sin, in this regard, would be reckless custody of your intellect, should you be vulnerable to error. Be vigilant in seeking the truth, study your Catholic faith in the important areas of salvation, authority, scripture, etc. and you will be fine.
God definitely wants you to be at peace, so likely He used the Protestant preacher for that purpose. He loves you and will continue to refine in you all you need to be fully in the Kingdom.