Hiya.. asap remove the battery, it is leaking. If you have side cut snippers you can cut the battery front and back and physically remove it. You will then need to remove the motherboard from the case and desolder the battery legs left in the mobo.
On ebay there is someone selling the coin battery replacement device that is very easy to install but you must have the mobo free from the case to do it correctly.
Please get yourself some 1024*4bit Zip fast ram! All 16meg of it if you can afford

Even 4meg will make a difference!
Any 50pin SCSI drive under 1gigabyte should work with your rom tower. Kickstart 1.3 and the onboard SCSI ship should allow the 1gigabyte drive to be formatted. If I remember correctly you should have the superkickstart roms in the rom tower, but its been a long time since I had my 3000 without 3.1ks roms in it

The missing SCSI terminator packets from the back sockets is ok, just use an external terminator, a good idea anyway as you should get yourself an external SCSI CD-reader/burner. Makes the Amiga much nicer to use, download all your wanted programs and utilities on the net-connected PC and burn to CD-rom.
http://amiga.resource.cx/exp/buddhaInternally if you want to use IDE I would suggest buying a Buddha IDE as it will autoboot under KS1.3 or above with an IDE drive upto 4gig in size. I have one in my A2000, 4gig IDE drive with IDE cd-rom chained from it as well.
Ethernet is available as a Zorro card, the X-surf is a nice RJ45 style network card with SANA2 drivers. Also has non-booting IDE ports and a clock port. Aridaine is older and harder to find now, but also a nice ethernet card.
http://amiga.resource.cx/exp/xsurf2Sorry but the mouse and internal floppy you will need to search on Ebay or maybe you can place a wanted add on
http://www.amibay.com/Amibay is an amazing resource for Amiga items... have fun with your new/old Amiga!
Az