Here's my 2 cents, I think others will agree:
1. If your unit has 4MB of CPU Flash (Master --> Utils --> About --> Config), then update to 4.70, if not, update to 4.61. I take it you dont have the RFX32 card, so you should be fine with 4.70, otherwise stick with 4.61 as 4.70 has some buggy code for the RFX32 card (no problems if you don't have the card).
2. Yeah, just like in other synths (like Kurzweil K2000 for example) the sample RAM is used to hold samples loaded from disk and is cleared when you turn the unit off.
3. Depends on how many samples you have. If you don't have a lot, I would suggest getting a small internal SCSI drive (around 4GB or so, bigger ones cost $$$). This way all you'll need is a SCSI cable and a SCSI controller card for your PC. This will also take care of the Emu <--> PC communication and you will be able access the internal hard drive on your PC.
However, if you have more samples (I have 1,493 sample CDs, from Akai to Emu to Kurzweil), I'd suggest getting either a SCSI CDROM drive or a large external SCSI hard drive (or better yet both!). What I did was I grabbed a SCSI hard drive enclosure off eBay for pennies and then got this drive:
http://www.stalliontek.com/ProductDetai ... I15-003200
and stuck it inside. Works like a charm. Just make sure you have all your settings set right (SCSI ID, termination, parity, etc), as SCSI is picky about this stuff. Google will be your friend in this case.
This way you can keep all of your most favorite samples on the external SCSI drive hooked up to the Emu and then run another SCSI cable to your PC and have it connected in a chain.
Note: Don't attempt to put a large SCSI drive in your Emu, it will burn your power supply out and you'll be out of $132.50 + shipping for a new one.
If you're tech-savvy you can install a separate power supply just for the hard drive. I used a Sunfone dual voltage universal PSU which takes anything between 90 - 264VAC and gives me 2.0A at 5VDC and 2.2A at 12VDC. I wired this baby in parallel to the main PSU after the power switch.
Another thing worth noting is that the Emu can take both IDE and SCSI hard drives internally. However, if you go for an IDE drive then you will not be able to use SCSI to browse it and manage samples -- you will need a SCSI drive for that, which is why I think you should go for an external SCSI drive to save yourself the trouble. This way you'd be able to take it with you to another PC and you won't have to worry about opening up or burning out your Emu. Just make sure you get a drive that can fit all (or at least all the favorite) samples.
Good luck!