Some thoughts for you:
I would look st upgrading to SBS 2003, remote support and working is much improved in this version. I expect that you will, at the very least, need to look to upgrade the memory on the server for this.
I would upgrade the workstations to windows XP or look at Linspire as a cheaper alternative. You may be able to get away with increasing the memory and replacing the HDD in the workstations rather than replacement.
Not sure if your dialup is modem or ADSL, I would suggest upgrading satellites to ADSL if do already. Perhaps looking at the ADSL bandwidth at the main office also. You may need to look at an ADSL router supporting VPN from the satellite offices perhaps.