The Pram battery can be replaced: it's a coin Panasonic Vanadium Pentoxide rechargeable battery VL2330 HFE of 3 volts. It's on the interconnect board and with a bit of soldering easy to replace.
As for 2.5" SCSI Hard drives: well good one's are very hard to find. You can buy non-working powerbooks on Ebay or so and hope the hard drive is still good but experience has learnt chances are slim the hard drive inside is still good.
Always test your hard drives with Apple HD SC Setup or another low level formatter like FWB to be sure the drive has no bad sectors.
If you can pick a brand: go for IBM, 2nd choice would be the larger Connor drives.
Nico