Ill go in reverse here. Firstly, Congrats! Songwriting is such a hit and miss thing that when you write your first song no matter how good or bad it is its an achievement in itself.
Secondly, I want to hear it and I am sure others do too like @Happy Blue
Lastly, for RCA to TRS its the way to go but if I am not wrong you want something that does Stereo although I could be 100% wrong here. I used an XLR to TRS (I think jack years ago and it was really good who knows what advancements have been made there). Suffice to say its easy and a lot of folks do it as the iLoud is very popular.