If you get a version that connects over an ethernet port and you have an ethernet port in the pc then there should be no (hardware) problems.
However I would not connect a Win98 PC via broadband if I could possibly help it due to the threat of the PC being taken over/infected etc by the mass of nasties that patrol.
At the very least, if you still want to attempt it , I would suggest :
1. Getting an ADSL modem with a built in firewall
2. Run a software firewall such as Sygate Free Personal Firewall
3. Run some Antivirus software
4. Don't use internet explorer as it is just too insecure - use something like Firefox or Opera instead.
5. Don't use Outlook Express as it also is just too insecure - use Mozilla Thunderbird or Eudora.
6. Use Adware/Spyware detectors at least once per week.
7. Make sure the Operating system and all applications are as up-to-date as possible in terms of patches.
Paranoid ? Me ? Too right when it comes to Microsoft Operating Systems