I would set Samba to authenticate users against your NT domain controller. This would only require you to have matching users in the /etc/passwd file. These users don't need passwords, however, just accounts on the Linux box.
Create a computer account in the domain for the Linux box. Then join the domain with this command...
smbpasswd -j 'domain' -r 'netbios_name_of_pdc'
Your smb.conf file should look something like this...
[Global]
wins server = '1.2.3.4'
name resolve order = lmhosts wins hosts bcast
workgroup = 'workgroup'
server string = 'servername'
netbios name = 'servername'
security = domain
password server = 'pdc'
encrypt passwords = yes
ChrisP
MCSE (2K/NT4), CNE (NW5), CCNA, Linux+, Server+, i-Net+, Network+, A+, CIWA