Dell 2000FP 20" LCD Problem/Questions

I've had this 2000FP for about a year and half. I've been running into some issues lately. The monitor will start to flicker and fade to a pastey yellow white color. The issue goes away when I adjust on the cables running into the monitor. Its like its a loose connection.....but the cables are securly put into the monitor. I'm using the VGA cables for the input on the monitor. I have a Radeon 9800PRO video card with DVI, but I haven't bothered getting a DVI cable. Would I notice an improvement in picture quality if I upgraded the cable to the DVI?

Second question. Think I should try and sell this monitor and get something better? I love 1600x1200. I once thought about upgrading to the 2001FP, but from what I can tell there isn't much of a difference? Is there a faster responce time? I don't play many FPS so I'm not really worried about ghosting....but then again, my computer is so freaking old I couldn't play FPS if I wanted. I've also been looking at the 2405FP and I'm thinking that wide screen at 1920x1200 would be amazing. I mainly do school work on my computer, but my school work includes AutoCAD and Photo Shop work. With those larger LCDs I would have to get a powerful graphics card to get the responces that I'd demand if i wanted to play at native resolutions. Ok, so I decide to sell the monitor....how much is the thing worth? I know people say its worth what someone will pay, but does $300 sound too high?