Eidorian said:
2. Installing more RAM. The RAM for this thing is dirt cheap. Would getting it up to say 256 MB help it?
As pointed out, it depends on how you want to use the system. The 8500 series has a physical maximum of 1 GB of RAM, so you have plenty of room.
The design of the 7500/8500/9500/7600/8600/9600 series systems was that if you installed DIMMs in pairs (there are two banks of four slots) the system will treat the two DIMMs as one single DIMM when writing to memory (it is called memory interleave). This is not a requirement of installing memory, but can have performance benefits.
3. Installing the RAM. I've dug around the case a bit. Getting to the RAM is nearly impossible right now. How do you do it?
Yeah... the 8500 uses the single worse case design of any that Apple has ever made. That case (used in the Quadra 800/840av and the Power Macintosh 8100/8500) is, to date, the only case design that I've ever walked away from bleeding after servicing one.
I currently own two systems with that case design, an 8500 (in storage) and a 8100 (my primary old Mac OS system). I actually use a 7500 (currently acting as a file and internal web server) rather than the 8500
because of the case design.
To remove the logic board you need to remove the restart button assembly (lower front corner), remove the processor daughter card (and any PCI cards), disconnect the AV unit ribbon (attached near the daughter card), remove (across the top of the logic board, from back to front) the SCSI ribbon, the power supply cable, the speaker cable, the CD-ROM audio cable, the floppy drive cable and a second power supply cable. Then unscrew the single screw in the center of the logic board, and push the board forward (towards the front of the system about half an inch (so the external ports clear the case). There is then a plastic tab between the SCSI cable connection and the first power supply connection that can be moved up (slightly) to let the logic board swing down and away from the system freely.
You then have access to the RAM, VRAM and L2 cache slots on the logic board. Be sure to hit the reset button (small red button near the daughter card slot) after installing RAM and the like.
Someone pointed out that it would be better to let a professional handle this... that is probably the best suggestion. I service Macs for a living, so I've done this countless times. But I've also gotten calls to help get systems back up and running after someone has tried to do this on their own with this case design.
Would there be any benefit of reinstalling the OS?...
Is 9.0.4 that much better to try to install it on my machine?
The reinstalling question... only if the system is not running properly.
As for putting a version of Mac OS 9 on it, I wouldn't. But then again, I'm not much of a fan of Mac OS 9.
My 8100 (which has 208 MB of RAM and a G3/500 upgrade) is running Mac OS 8.6. So is my PowerBook 2300c (which has 56 MB of RAM). Why? Because 8.6 was (in my opinion) the peak of the old Mac OS in terms of performance and stability.
The only reason that I have ever recommended installing Mac OS 9 on systems that could run Mac OS 8.6 is to run apps that require Mac OS 9.x.x (like iTunes). Otherwise, Mac OS 9 is a crash prone system that is also a terrible memory hog (64 MB of RAM is the absolute minimum I would install it on, and usually I recommend 128 MB).
My 8.6 systems rarely give me any problems where as I get calls every couple weeks for the Mac OS 9 systems in use by my clients.
Still, if you are going to put 9 on that system, I would suggest 9.1. It was the most stable of all the 9.x.x releases. You can
force 9.2.2 onto that system, but I wouldn't suggest it (unless you absolutely have to have 9.2.x to run some piece of software you need).
Just one last question. What's the best Classic web browser available?
While I hate recommending anything Microsoft,
Internet Explorer 5.1.7 is a nice browser... but just like the Mac OS X version, it is painfully out of date. There is also
Netscape Communicator 4.8 (also very out of date) and
Netscape 7.0.2 (which is pretty current, but tend to be a little unstable... even for a browser).
There a couple ports of Mozilla (
1.2.1 and
1.3.1) that should work, and versions of iCab and
Opera.
Hope that helps out a little.
Be CAREFUL with the connectors, especially the ones hiding inside the machine, not on the top edge where most of them live. Go to Lowendmac.com and look up the model - you'll probably find good takeapart instructions there. 
