Hi.
A tube amp and a cab, regardless of the quality, is a steal for that kind of money. IMHO anyway.
Assuming obviously that the tech knows his stuff and is offering the stack to be used with bass (100W +).
A few questions for Your tech:
Is it a CP or vintage?
Is it a Bassman (RCA) clone or something fancier?
For that price, it's probably not re-capped (if vintage), and comes with crappy tubes.
For how much will he service it with quality tubes?
Ask him these questions and if possible, try to get some pics as well.
In any case, if the tech is a stand up guy, he'll be up-front with You and wouldn't probably be offering it to you in the first pace if it wasn't a good one.
Edit:Well, I took Your word about it being a rare amp with no information on the net, here's some:
http://www.drtube.com/guitamp.htm#Elk
Regards
Sam