I think you would have no problem running OS 9.1 on that computer. There are people who have even mangaged to shoehorn 9.2 onto non-g3 macs.
As far as 802.11b is concerned, I'd download this driver:
http://www.ioxperts.com/pr/2003/1205.html
And buy one of the cards it supports:
- 3Com AirConnect PCI 777A
- Belkin F5D6000
- Eumitcom WL11000, SMC2602W, Addtron AWA-100
- Global Sun Tech GL24110P
- Linksys WDT11
- Longshine 8031
- National Datacomm NCP130
- Netgear MA301- Siemens SpeedStream SS1023
- Nortel emobility
- US Robotics USR2415