I'm a design engineer at a temperature monitoring company (not a sales guy, I asked 'em not to bug you) and could probably give you a suggestion or two for your wiring etc. (A sales guy saw your post and asked me "how Slashdot worked" so I told him I'd contact you.)
Of course, I think in terms of our devices - we have a 16-channel monitor that's rated for installation down to -40 C (-40 F) and isn't terribly expensive ($499, I think, but since I'm a tech guy I don't know for sure) plus $50 per probe. Max run on a probe is half a mile (2600' or so) over cat5 (or you can buy more expensive long probes.) If you use someone else's hardware, look for industrial-temperature rated hardware if the PCB is going to be inside the cooled area. Mechanical parts (e.g. hard drives) should be avoided at all costs.
If you have any more specific questions I'd be happy to answer, even if you don't use our hardware. Our stuff is all Ethernet interfaced, for an example look at:
XML for computers:http://em1.sensatronics.com/xmlconfig/http://em1.sensatronics.com/xmldata/
Perl scripts are available that grab data from the devices. Note that they don't log data (normally... there's an HTTP POST feature that does log up to 18 hours of data) but are designed to get the data into PC-land as quickly as possible. They run a tiny embedded OS, Linux is a bit heavyweight for cheap 256K flash hardware. (uCOS/2, not that it matters.)
--Drew Van Zandt