For some information on Amiga network cards check
here.
In an Amiga 2000 you can use Zorro2 expansion cards, not PCMCIA. Those are for A600 and A1200 only. I paid ~60EUR for my AriadneII network card. A new XSurf card would cost ~100EUR.
As for a keyboard interface see
here (40USD).You will also need a TCP/IP stack for connecting to your LAN, such as Genesis (included with OS 3.9). I think the version numbers you said are WB2.x isn't it? It would be better to upgrade to OS 3.9 (~40EUR), but then you would need Kickstart 3.1 (~30EUR). You need a CD-ROM for that (~60EUR for a SCSI drive?). To use OS3.9 you'd be best of with a graphics card (cheap second hand one: 50EUR?).
So total cost:
100+40+40+30+60+50=320EUR
(1EUR~1USD).
*whoa*...thats a load of cash :-).