The RAM is nothing special, it's just a regular 30-pin SIMM, 1MB each. The spec
says it's 150ns, which is slow. Most are 120ns, some can be 80ns. Faster won't do you any good, but slower (like 180) would be bad.
As far as caution goes, you don't have to worry about a whole lot, other than electro-statically discharging yourself first. Just touch the metal chassis and call it good (and don't move far). The fact that the computer is "old" has nothing to do with it, it's actually very easy, a non-computer oriented person could be walked through it. A SIMM is a Single In-line Memory Module, most these days are DIMMs for Dual In-line Memory Module, meaning there are electrical connections on both sides of the module, and usually chips on both sides.
1. Obtain a T-15 Torx driver, about 15cm long. Notice I didn't say "allen key".
2. Remove all connections to the computer.
3. Remove the four torx screws, there is one near the mono speaker out, one near the ADB ports, and two inside the carry handle cavity.
4. Place a protective blanket over a couch or a bed. Invert the Mac so the CRT is facing downwards, and use inertia to pull the rear cover off. (Can take practice)
5. Discharge yourself against the chassis.
6. The motherboard is on the bottom side of the machine. Peering inside the machine, disconnect the motherboard power port, the floppy and HDD cables to the motherboard.
7. Look at the bottom of the chassis. The motherboard slides in two rails, and it has to slide backwards a bit before it can come out of the slot on one side. As you take it out, disconnect the speaker.
8. Your motherboard likely will not look exactly like this one, but similar:
This one has an accelerator. For our purposes, it's fine. Your RAM slots are on the front of the board:
You can see that one SIMM is already "half out" and is not retained by the keepers.
9. What you do next is to look carefully at the SIMMs. There are two plastic keepers on each end of the SIMM, these have to be carefully pushed out of the way, then the module rotated out towards you. Do not
break the keepers.
10. It's a good idea to clean the RAM contacts on both the memory module and the motherboard with 99% alcohol, in fact the entire motherboard would be better. Even if you don't have it on hand, 99% alcohol has many uses outside this task.
11. To insert the new memory, put the SIMM contacts into the slot, then press down and push back into the keepers. It should just *snap* in. Double check your work, then reconnect the speaker connection, reconnect power port (if you can) then reposition the motherboard on the rails, and slide it back in.
12. Reconnect the FDD and HDD cables, the power port, then put the EMI shield back on underneath the motherboard, put the rear cover back on and replace the screws. They don't need to be mega-tight -- just snug is fine, they are metal screws going into plastic, so don't strip them (the bottom screws are going into sheet metal).
As far as getting some SIMMs, I just so happened to have a large quantity of 1MB modules I need to get rid of. While you are in there, it would be a good time to get ahold of a 1/2AA PRAM battery with solder tabs, and put a new battery in. Even better is get a battery holder.