upgrading 2.7 -> 2.8 with limited space

[j_(_at_)_nabu_(_dot_)_falooley_(_dot_)_org (Jason Lunz)]

I'm running openbsd on my DSL firewall on a small i386 box. I did the
initial install from CD, and I'd like to upgrade to 2.8 over the
network. What's the most straightforward way to do that, considering the
limited space available?

[naburus][11:32am](1) $ df -h
Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/wd0a      29M    17M    11M    61%    /
/dev/wd0d      38M   4.8M    32M    13%    /var
/dev/wd0e      46M   1.0K    44M     0%    /tmp
/dev/wd0f      20M    80K    19M     0%    /home
/dev/wd1a     197M   161M    26M    86%    /usr

In the past I've copied the CD sources to a larger machine inside the
firewall, nfs-mounted it from the OpenBSD machine, and upgraded that
way. Can I do that to upgrade to 2.8 easily, or do I need to worry about
bootstrapping the gcc upgrade?

I can also just get the distribution set and put it on an nfs export,
but can I install it on the firewall with just an ssh session? I don't
have a monitor on the openbsd machine, and it would be nice to upgrade
it without having to find one.

suggestions much appreciated,

Jason