This guide is a bit old, but I still use it and if you have the version of the amv app that the guide links you to it will walk you through switching your aspect ratio to 16:9 from 4:3.
http://www.animemusicvideos.org/guides/ ... atios.html
You can account for the change in your video editor too, but it's a bit harder to do and could potentially stretch your footage. There was a tutorial on a forum I used to visit on how to do this, but unfortunately the forums been shut down and I can't link you to it.
Subtitles there isn't much you're going to be able to do to remove them. I would suggest if you have the funds to purchase the DVD's you're footage quality will be hire and it will make using the programs you need to change the aspect ratio easier to use.
Regardless what you do you're going to have to upscale the footage so you will lose some of the edges of your frame, and it is possible that your subtitles will get cut off while up-scaling to the 16:9 aspect ratio.