It was not done by immersion. I bent over the baptismal font and the Roman Catholic priest poured water over my head as he pronounced the Trinitarian formula.
Do I then need to be rebaptized by immersion?
No. If you look at the earliest recording of Baptism (outside of Scripture) in the Early Church (The Didache) you will see that sprinkling is just fine.
" But concerning baptism, thus shall ye baptize.
7:2 Having first recited all these things, baptize {in the name of the Father and of the Son and of the Holy Spirit} in living (running) water.
7:3 But if thou hast not living water, then baptize in other water;
7:4 and if thou art not able in cold, then in warm.
7:5 But if thou hast neither,
then pour water on the head thrice in the name of the Father and of the Son and of the Holy Spirit.
7:6 But before the baptism let him that baptizeth and him that is baptized fast, and any others also who are able;
7:7 and thou shalt order him that is baptized to fast a day or two before.
8:1 And let not your fastings be with the hypocrites, for they fast on the second and the fifth day of the week;
8:2 but do ye keep your fast on the fourth and on the preparation (the sixth) day.
8:3 Neither pray ye {as the hypocrites,} but as the Lord commanded in His Gospel, {thus pray ye.
8:4 Our Father, which art in heaven, hallowed be Thy name;
8:5 Thy kingdom come;
8:6 Thy will be done, as in heaven, so also on earth;
8:7 give us this day our daily bread;
8:8 and forgive us our debt, as we also forgive our debtors;
8:9 and lead us not into temptation, but deliver us from the evil one;}
8:10 for Thine is the power and the glory for ever and ever.
8:11 Three times in the day pray ye so."
Here's the link:
http://www.earlychristianwritings.com/text/didache-lightfoot.html
Peace!
WM