H.264 videos on Xbox 360

Hey everyone. I have recently received a few very large H.264 movie files from a friend. I would like to play them on my 360. I just had a few questions...

The files were originally .mkv, so i am converting them into mp4's. My friend says that they are full hd resolution (1920x1080), but my tv is only 720p. If I convert these files without changing the resolution, will my xbox effectively play the files at a 720p hd resolution? I would change the resolution when converting, but I want to be able to play them later on a full hd tv. Really I just want to know if these files will look the same as if a blu ray was being played on a 720p tv.

Also, I have heard that the max. file size for mp4 videos is 4GB. Does anyone know of an easy way to split my mp4's after they have been converted?

Finally, does anyone know of a way to check the native resolution of a video file? These files were originally from a blu-ray disk so they should be in full hd. I just want to confirm that because when I play the videos on my laptop (1680x1050), they look sort of funny. The files are all greater than 10 GB so I think they are full hd, but i would really like to get some sort of confirmation.

Thanks for any help you guys might have.