does an ss1+ have a built in frame buffer or would i have to buy
   one of those as well?

you'd need to find a frame buffer.
   
   1. what are the chances of getting an ss1+ on a 100baseTX network?
   do i need an SBus card?  any idea on how much this would cost me?

netbsd/sparc doesn't support any of the 100bt cards available for the
sparcs so while you can but them you won't be able to use them :)
   
   2. what about having an ss1 as a gateway box with ipf and ipnat.
   it has one 10 mbit connection but can i add another?  via an SBus
   slot?  how much would another 10 mbit adapter cost me?

again, you'd need an sbus card (like you say).

i don't know what the prices of either of there are sorry.  you can
probably find them second hand for a fairly reasonable price..
   
   3. any stability problems with netbsd on ss1+'s?

nope.  an ss1+ was my original netbsd/sparc machine >4.5 years ago
now.. it was faithfully working for it's current owner until a few
months ago when some evil people stole it :(
   
   4. i assume that it has a fast narrow scsi-2 adapter with it.
   what about using external scsi disks?  any way to use a wide or
   ultra disk with an ss1?

that's slow narrow, sorry :)  you can get fast/wide/differential
cards for the sparcs but again i don't think netbsd supports any
of them  :(
   
   5. anything that doesnt work that i should know about?  does X
   work?  etc...

X for the sparc has been working stabily for more than 3 years (i
forget exactly when started working).
   
   i may be over doing it here with the talk of using ultra wide
   scsi disks and 100 mbit networks with an ss1+ but i just wanted
   to check into it a little

a bit.. the ss1+ isn't a speedy machine as you'll find out :)
   
   any good info sources on where i can get details about the
   hardware on ss1's?  the bus type, add on adapters, 
   scsi adapter info, ethernet adapter info, etc 

the sun news groups are good.  there is also a "sun hardware" faq
floating around the net -- ask a search engine for it..  you can
get a reasonable list of what devices netbsd supports from reading
the web pages and/or INSTALL document from the latest release.