I don't know the answer to your RAM question, but maybe someone else here will be able to answer it. When I need to replace or upgrade RAM, I ask the techs at the store every time just to be sure.
You must need quite a bit more memory than I do.
Unlike a lot of people, I've never even come close to using a quarter of it on any of my computers, and the SE/30 works fine. It will probably end up getting more than a quarter of its memory used, but it should still be sufficient.
Finding parts is not as hard as it seems. I had a lot of success with a wanted ad on Craigslist asking for old Apple parts and accessories. Someone who used to be an Apple technician gave me a lot of stuff for free, including software I'd planned to buy, and Goodwill is another good source.
Not too long ago Goodwill got a contract and now they carry computers. There are always computers at the Goodwill store here, usually quite a few of them, and they get Macs pretty often. They get so many old Macs that's I've had to pass up quite a few and just start cherry picking them. I even got a motherboard for my eMac G4 for 99 cents there, and mine could use a new one. Actually, I've picked up several potentially useful Apple/Mac motherboards, all for only a buck or two at Goodwill and yard sales. Hopefully they work, and if not, they're still good for components. Then there's always eBay.
I picked up an ImageWriter II to go with the SE/30 for $10.00, and it'll be easier than borrowing the printer off the 7600/132. The printer with the 7600/132 was a freebie as a result of the wanted ad on Craigslist. (Earlier in this thread I asked about a cord to connect the printer to the SE/30, but got one off eBay, so that's solved.) The printer works, and printing cartridges are available on line. It's just a little slow. OK, really slow, but that's easy enough to work around.
Everything in computers eventually becomes outdated, and lots of people want the latest, shiniest gadget. But many of those older items can still meet people's needs and get the job done nicely, depending on what they're looking for and how they will use it.