Optiplex G1 400L+ processor specs, external CD drive compatibilty questions

Hi, I really need some help on figuring out this one ASAP so I'd really appreciate your help.  I am trying to take advantage of the time I have left in the US to order equipment before I return to Haiti in mid-February in a few weeks.

I am trying to equip myself to be able to fix an old Optiplex G1 400L+ which is in Haiti and other old computers that may cross my path.  I think that it has the low-profile chassis (I looked at the service manual and seem to remember only 3 expansion slots).  I took it in to a shop in Port-au-Prince with my licensed version of Windows XP SP2 for them to install it, upgrade the memory, and install a sound card.  I had two out of three done successfully, but got hoodwinked on the OS installation, where an unlicensed version was installed instead and my licensed version swiped by an employee.  I tried to do a Windows update through the internet and an unlicensed version of XP was detected, so the computer started to have problems after I left for a two month visit to the U.S.  I need to be able to equip myself so I can do a fresh install and also troubleshoot around other old computers that may cross my path that similarly do not have a CD-ROM.  I work in a popular neighborhood and do computer classes and minor fixes to reciprocate the help I receive for my ethnographic research and presence there.  I do not feel very comfortable opening up desktops so I need to know what external USB CD drives I may connect so I can possibly boot from the CD drive if the system crashes or just do simple installations from the CD drive.

The information I gathered on the specs before I left Haiti for a visit to the U.S. are:

Intel Pentium II processor (I do not have the MHz)

256MB RAM (I had this upgraded from 128)

HD Capacity 5.99GB

Other info:  "Computer x86 Family 6 Model 5 Stepping 2, AT/AT Compatible", Bios Revision A06, 3 COM 3C918 Integrated Fast Ethernet Controller (3C905B-TX Compatible)

My questions are

1.  Can I figure out the MHz processing speed with the information I have on the unit, that is, was there a standard Pentium II processor of a specific MHz installed on the 400L+ model of the Optiplex G1 series?

2.  If not, what are the various MHz speeds of Pentium II processors?

3.  Are there external USB optical drives out there compatible with the Pentium II and 256MB of RAM?  I really only need to read CDs, and notice that many external optical drives on the market require at least Pentium III.  Could I be assured that if a CD drive is compatible with Pentium II, it will be compatible with its various incarnations at different MHz?

4.  Where could I find such a drive?

5.  The system clock does not stay consistent after being shut off because I believe the battery is dead.  I do not have the original system documentation--was there a standard battery that I may find to replace this and if so, where would I purchase it?

6.  I do not know if the floppy is reading well--but should I procure the 6 floppy disk set for this computer and how can I do so?

I am a graduate student so low-budget leads are especially appreciated.  Thank you in advance for your help.