I've never messed with the timing chain or guides on my 03 mach 1 but I did change the lifters/lash adjusters (all 32 of them) and it surprisingly wasn't that bad. Like you said, it was definitely a chore just to get enough access to actually remove the valve covers. If you're already in there you might check your lifters to make sure none of them have "collapsed" (assuming they are hydraulic) as well as the rocker arms for play. However, I don't know how it easy it is to remove the rocker arms on the 3 valves, on the 4 valve all I needed was a flat head screwdriver, not at all what I expected but it worked great. I actually bought spring compressors and a few other tools that I thought I would need but didn't.
It's always a good feeling when you hear a noise you know isn't right, do some research, tear it apart, find a problem and get it taken care of diy style. Good luck!