Sorry for that - but normally the package will not break your system!
The libs are new and will not override any existing versions (under /lib).
Before you reboot the whole system, you should start squid manually to look for errors.
If something goes wrong then you are able to reinstall squid-2.6.21-4 (or restore the modules you have replaced before).
The squid-package-2.7.4 is only for pfsense 1.2 based on freebsd 6.2/6.3!!!
squid is working on my alix 2C2-board:
# ps -aux|grep squid
root 1177 0.0 1.0 5444 2568 ?? Is Tue09AM 0:00.00 /usr/local/sbin/squid -D
proxy 1179 0.0 23.9 65276 60692 ?? S Tue09AM 6:32.04 (squid) -D (squid)
proxy 37959 0.0 1.6 34904 4136 ?? Is 12:00AM 0:00.34 (squidGuard) -c /usr/local/etc/squidGuard/squidGuard.conf (sq
proxy 37960 0.0 1.6 34904 4064 ?? Is 12:00AM 0:00.17 (squidGuard) -c /usr/local/etc/squidGuard/squidGuard.conf (sq
proxy 37961 0.0 1.6 34904 4004 ?? Is 12:00AM 0:00.15 (squidGuard) -c /usr/local/etc/squidGuard/squidGuard.conf (sq
# squid -v
Squid Cache: Version 2.7.STABLE4
configure options: '--with-aufs-threads=10' '--bindir=/usr/local/sbin' '--sbindir=/usr/local/sbin' '--datadir=/usr/local/etc/squid' '--libexecdir=/usr/local/libexec/squid' '--localstatedir=/usr/local/squid' '--sysconfdir=/usr/local/etc/squid' '--enable-removal-policies=lru heap' '--disable-linux-netfilter' '--disable-linux-tproxy' '--disable-epoll' '--enable-auth=basic ntlm digest' '--enable-basic-auth-helpers=DB NCSA PAM MSNT SMB LDAP YP' '--enable-digest-auth-helpers=password ldap' '--enable-external-acl-helpers=ip_user session unix_group wbinfo_group ldap_group' '--enable-ntlm-auth-helpers=SMB' '--enable-negotiate-auth-helpers=squid_kerb_auth' '--with-pthreads' '--enable-storeio=ufs diskd null aufs coss' '--enable-delay-pools' '--enable-snmp' '--enable-ssl' '--with-openssl=/usr' '--enable-htcp' '--enable-forw-via-db' '--enable-cache-digests' '--enable-wccpv2' '--enable-referer-log' '--enable-useragent-log' '--enable-arp-acl' '--enable-pf-transparent' '--enable-follow-x-forwarded-for' '--with-large-files' '--enable-large-cache-files' '--enable-err-languages=Armenian Azerbaijani Bulgarian Catalan Czech Danish Dutch English Estonian Finnish French German Greek Hebrew Hungarian Italian Japanese Korean Lithuanian Polish Portuguese Romanian Russian-1251 Russian-koi8-r Serbian Simplify_Chinese Slovak Spanish Swedish Traditional_Chinese Turkish' '--enable-default-err-language=English' '--prefix=/usr/local' '--mandir=/usr/local/man' '--infodir=/usr/local/info/' 'i386-portbld-freebsd6.2' 'build_alias=i386-portbld-freebsd6.2' 'host_alias=i386-portbld-freebsd6.2' 'target_alias=i386-portbld-freebsd6.2' 'CC=cc' 'CFLAGS=-O2 -fno-strict-aliasing -pipe -I/usr/local/include -I/usr/include' 'LDFLAGS= -L/usr/local/lib -rpath=/usr/lib:/usr/local/lib -L/usr/lib' 'CPPFLAGS='
# uname -a
FreeBSD pfsense.netview.de 6.2-RELEASE-p11 FreeBSD 6.2-RELEASE-p11 #0: Sun Feb 24 16:38:29 EST 2008 sullrich@builder6.pfsense.com:/usr/obj.pfSense/usr/src/sys/pfSense_wrap.6 i386