When I bought my car, I had intended to replace the stock unit & speakers anyway. They're OK, but that's it - just OK.
As fate would have it, the drivers front speaker would cut out on my 1999 SE also. It turned out to be the head unit had some fried components - I suggest you may be needing a new unit too.
You should do some research before you buy a "cheap" unit. Look for some THD (Total Harmonic Distortion) numbers - lower is better and there is no substitute for quality sound. JVC seems to make some really nice sounding CD players that can be had in the $120 to $250 range. They put out 45 watts per channel or more - Not bad. I have also found that the tuners in the JVC units are pretty darn good as well.
For a simple install, Best Buy will install for free around here, or you can just purchase a JVC to Ford adaptor & plug it in to your existing harness plugs - EASY. That way you can re-install your factory stereo if you ever trade in the car.
A little more than $0.02 worth.