First of all, welcome to the Boards! I'm a former Calvinist myself (from the Presbyterian Church in America). You have many fewer reservations than I first did!
Confession is a sacrament (a mystery) of the Church through which sins are forgiven. This was instituted by Christ, who gave this power to the Apostles, who in turn empowered the episcopacy and priesthood to serve this function as well. The biblical basis is found here:
"Whose soever sins ye remit, they are remitted unto them; and whose soever sins ye retain, they are retained." (John 20:23)
Does Christ require, absolutely, a sacramental confession? The answer is no, not absolutely. There are even saints, martyrs of the Church who died for Christ that were only catechumen, who had not yet experienced confession or even baptism for the forgiveness of sins, and yet they obviously have received it, as they are numbered among the saints. However, confession is the normative sacramental route that we obtain forgiveness, as given to us by Christ Himself. This relationship with a priest also enables us to struggle with our sins before someone, that we are encouraged in our troubles.
Actually, the classical reformers (I don't know what Reformed tradition you come from) also forbade worship with instruments. Perhaps you do not come from such a classical Reformed background, but they're out there. Honestly, my main reason for defending against the use of instruments is the liturgical rite served in the Church...the Byzantine Rite is meant to be a capella, and sounds down right weird without it. Why change this? It is what we have received, and it is beautiful. Latin services would also be much more beautiful without that horrific organ and MUCH more Gregorian chant than is used in today's services.
As for Sola Scriptura, it ironically has no biblical basis. Ialmisry quotes Acts, which admits to the need for interpretation of the Scriptures by an outside source, but there are even more verses that make it clear that the Scriptures are not the be-all-and-end-all of Christianity:
But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth. (1 Timothy 3:15)
"Therefore, brethren, stand fast, and hold the traditions which you have been taught, whether by word, or our epistle." (2 Thessalonians 2:15)
The first verse points to the Church as the "pillar and ground of the truth", not the Scriptures. The second holds the "word", the spoken word, of that which the Church in Thessalonica was taught in person (which we do not have) and the epistles written (which we do have) as equal. We have the Scriptures, the epistle, and we have the framework that fits in, the Holy Tradition of the Church, which was taught from the beginning by Christ, to His Apostles, etc.
The Scriptures, as we know the New Testament, was not even a canonized work until at least the 4th century. Many hundreds of books were written in those centuries, and only 27 made it into the canon. Many of those works are now considered good for Christians to read (like the genuine epistles of St. Clement, the Didache, the writings of St. Ignatius the Shepard of Hermas, etc.) that WERE considered, locally, as Scripture and read at the holy services. along side books that we now consider part of the New Testament. Likewise, others we now call Scripture had a bit of a hard time getting that recognition, like St. John's Revelation.
