I have a Packard Bell Legend 204CD system, which has been in my possession for about ten years. It's a desktop form factor and has a PB450 motherboard with a riser for 3 ISA slots, a 486DX2/66, 4MB of onboard RAM + 4MB on a SIMM, 545MB hard drive, onboard Cirrus Logic GD5428 graphics, and a pretty high quality and compatible SBPro clone+14.4 modem ISA card which is identified in Win95 as a "Sound Galaxy Washington 16" while all the software that came with the computer calls it a Voyetra Sound144AM-- while it is really an Aztech card.

About two years ago the battery died and it hasn't worked right since because it can't hold on to any settings. Now I'm finally taking a look at it and along with fixing the battery I'm going to upgrade it pretty heavily if I can. I originally intended to build a new 486 system from scratch, but I believe it will be more cost effective to work with this one since I already have most of what I need, like a case, motherboard, etc. There's also the nostalgia factor, as I played with this thing at my grandmother's house as early as the age of 4. I have a lot of concerns about upgrades, however, due to my lack of knowledge about the hardware:

-I'm not sure I understand how the battery replacement works. It had a soldered on BR1225 battery originally, which I removed. The manual for the computer states that I can attach an "optional off-board battery" at (J30) but doesn't explain anything else. It just says to attach the "external battery cable" there. What type of battery would this mean? I was told on another forum a while ago that I would be able to solder a 2xAA battery holder to the pins there and it would work, but I would like confirmation before I bust out the soldering equipment.

-I am curious if the machine would take a Intel DX4-100 or Am5x86-133. The machine itself is from March 1995, so after the DX4 release but before the 5x86. The manual only states that it has support for up to the DX2-66 as well as Pentium Overdrive processors. However, the board has jumper settings to use either a 3.3v or 5v processor, so at least technically it should be able to take either processor when the board is also set to the 33mhz bus speed. However, I'm not sure how this works-- whether these CPUs need specific BIOS support or not. I know 5x86s were used to upgrade older 486s that would probably not have specific 5x86 support, but I would like some field knowledge about this.

-The board also has the ability to upgrade both the cache and VRAM, but the information is not the best.
For the cache, it has 8KB onboard but can upgrade all the way up to 512KB. To get to 512KB it simply says "Obtain [4] 128Kx8 (20ns), [1] 32Kx8 (15ns), and [1] 64Kx1 (15ns) cache SRAM chips" and shows where they go. However, I went to look up these chips and they come in all sorts of shapes and sizes so I have no idea what they want. They appear to be 32-pin chips by the diagram but that's all the information I can really get from this.
For VRAM, it wants two 256Kx16 (70ns) ZIP DRAM chips "with 2 CAS lines (symmetrical)", and I can't even find these. Should I even bother or am I just not looking hard enough? (I'm interested in the higher resolutions for Windows, the integrated video isn't really all that bad of a performer, and it keeps one of the few ISA slots free-- but if there's a decent ISA card out there that will be cheaper than working with this, then I'm game)

I have some okay-ish scans of manual pages if they are needed. Thanks in advance for any help you can give. As I've said before, I'm not really a great hardware guy yet, especially the further back I go.