Galatians-Week 1-A New Gospel?

Here's the next part of the letter, Galatians 1:6-10:

6I am astonished that you are so quickly deserting the one who called you by the grace of Christ and are turning to a different gospel— 7which is really no gospel at all. Evidently some people are throwing you into confusion and are trying to pervert the gospel of Christ. 8But even if we or an angel from heaven should preach a gospel other than the one we preached to you, let him be eternally condemned! 9As we have already said, so now I say again: If anybody is preaching to you a gospel other than what you accepted, let him be eternally condemned!
10Am I now trying to win the approval of men, or of God? Or am I trying to please men? If I were still trying to please men, I would not be a servant of Christ.

Paul's letters usually start out with a peaceful greeting, an encouraging word to struggling groups of Christians, but, to me, it seems he's just a little put out with the Galatians...the churches that he'd established and invested the time to teach the gospel as it had been directly revealed to him...these believers were being misled...they were deserting. Different translations will have different words but Paul was amazed or astonished that they were deserting, willfully leaving the gospel.

7. So what's this "new gospel" we've been hearing about?
Unfortunately, we don't have a letter from the Judaizers outlining their dogma, but it's easy to see that it's contrary to Paul's message of salvation by grace through faith. The Judaizers agreed that Christ was the Messiah, but they wanted to make salvation for the Gentiles contingent on a type of conversion to Judaism or, really, to make Gentiles subject to the rules of Judaism (specifically, circumcision) before they could be saved.

It's easy to see why the Galatians would have been, at the very least, confused by the Judaizers. I also sometimes wonder about how easily I am saved. Simple faith is all it takes, but it seems like there should be so much more. And the Judaizers have a simple solution to that: yes, you can say that Christ is who He said He was, but then why don't you also try to live under the law perfectly like we've tried and failed to do for centuries? (I don't know if they really said that. I may be paraphrasing.)

Do you see why Paul reacted to strongly? A righteous Pharisee who knew the law and did his best to live it, converted and taught personally by Jesus Christ himself, committed to spreading His gospel...to be confronted again by the law, creeping its way back into the early church to confuse the new believers in Galatia.

What was Paul's gospel before conversion? What is his purpose after conversion?
What kinds of substitute gospels to people preach today that tempt people to depend on something besides Christ for security and salvation?

The MacArthur NT Commentary says this:

Satan's primary target for false teaching is the doctrine of salvation, because if people are confused about that they have no way of coming to God in the first place and thus remain under Satan's influence and control. He teaches lies about church organization, Christian living, the Lord's return, and many other things. But his first concern is to undermine the heart of the gospel, which is salvation by grace, made possible through the Person and work of the Lord Jesus Christ.

We can talk about whether Paul was changing the gospel to make people like him tomorrow...but I'm thinking "No" is the answer.