Logo Problems In LiteJazz Theme

Hi, I need some help with the LiteJazz theme.

I'm trying to put in a custom logo, and I keep having a large space open up between the logo and the primary links. I found out that the situation basically was due to the three elements that make up the Lite Jazz logo: mast-bg.png, mast-l.png, and mast-r.png

However, when I try to change these picture files to different picture files -- nothing changes (I've fiddled with the caching- still no changes.)

My question is: is there a way to change these files? Or is there a way I can get rid of these elements altogether and just have my own logo?

Thanks!