Paul knows how to pack his words full, that's for sure. Rather than get all line-by-line like a commentary might do, I want to focus on the things that risk being missed.
See how, at the end of the list of blessings (1:13-14), Paul broadens the conversation? He has been talking in "we" language for awhile; he switches to "you also" to include his readers now. How did "you also" get involved? By hearing "the good news of your salvation." There's a phrase that needs to sink in. They did not hear "a conviction of their sin, followed by an explanation of Christ's sacrifice, which, if we make sure they believe certain things about it, would then cause Christ to be accounted on their account, after which they would then be ok with God (as far as we know)." No, not at all; instead, the message they heard was "the good news of their salvation."
How many layers we usually put between Christ and salvation, how much we try to involve ourselves, how much we tone down the power of God and the immediacy of God's power and presence in the message of Christ. They did not hear the gospel as a proposition about how to get saved which was then set up as a stop-point, an obstacle that they had to "accept" (surmount). Instead, they heard that God's eternal purpose is for our good, that for Christ's sake God forgives them and adopts them as his own children and holds a blessed future for them. They were not told a theory about how it worked and asked to decide if they believed it; they were told what God has done for the world in Christ Jesus and what he still intends to do, and they believed it. That is how it goes with the heart that is ready to hear, when we proclaim the good news of their salvation. It is typical for us to hold back and proclaim the theory and wait at the checkpoint to see who passes by assenting to the proposition. By making it a stopping point ("Do you believe this? Are you sure?") we weaken the proclamation to a proposition. We behave as if the blessing depended on our understanding, and the power of God waited on mortal minds to catch up. More often we should proclaim God's goodness straight and undiluted, and throw open the door. They heard "the good news of their salvation" and believed it.
Paul also renews the theme of holiness here, which he comes back to throughout the whole of the letter. By the time we get to v. 13, Paul has already brought up the holiness of the believers a couple of times. He called them holy ("saints") in his greeting; he tells them that one of the blessings we have in Christ is to be holy and blameless before God. Now Paul introduces the presence of God not only in the heavenly realms or in Jesus, but also within themselves, as the Holy Spirit within them is called the deposit (or earnest money) guaranteeing their redemption. (I wonder if "down payment" would suit, as a translation?) And here -- bless the Pentecostals, as with any group their public figures could use a better image -- but the people who talk most loudly and most publicly about the Holy Spirit don't seem to grasp the idea of holiness, or that the Holy Spirit is part of the picture of our becoming holy. We'll see in the rest of the letter what Paul means by us becoming holy; it's not exactly what we'd expect.
Paul also renews the theme of riches and inheritance. He uses that language often in this letter, but it's not about money. We hear of the riches of God's grace (1:7); if the Holy Spirit is a deposit guaranteeing our inheritance, that suggests that the majority of the riches of God's grace are still unknown and unseen. A few glimpses forward in the letter may be in order, since I don't know if I'll really bring up the "riches" theme every single time Paul does. The riches are "the glorious inheritance in the saints (the holy ones)". The riches of God are "his great love for us" -- he is "rich in mercy" (2:4). Our inheritance is "the incomparable riches of his grace" and particularly "the incomparable riches of his grace, expressed in his kindness to us in Christ Jesus" (2:7). The "richness" of God is expressed in his wealth of kindness. And our holiness -- the Holy Spirit -- is given us because of God's mercy to us in Christ; that is part of our inheritance. (All of which puts an interesting light on the parable of the talents, in which the wealthy master gave some of his riches to his servants, to see what they would do with them.)
Paul keeps this theme going strong until he reaches his ultimate point with it. "His glorious riches" are again tied to the Holy Spirit and Christ dwelling in our hearts (3:16-17). We are called to grasp one particular point of God's vastness: the vastness of his love for us (3:18-19). Once we have grasped the graciousness, kindness, and overflowing generosity of God -- his eagerness in blessing, his plan and purpose for our good, the incomprehensible scope of his love -- then Paul moves forward with the implications that this very same God is the one dwelling in our hearts.