Walk away.
You may be lucky that the problem is trivial to find and fix, or the scope could be a complete disaster with parts/boards missing or a completely dead CRT. Old analog Tek scopes in working order are generally very nice instruments. The problem with them is that they are complicated beasts, frequently built with many custom or hard to find parts.
As a beginner you may have better luck troubleshooting and fixing a simpler, less complicated scope, like a <= 20 MHz Hameg or maybe a Philips (no idea how common these are down under).
Tek scopes are not dirt cheap here in Denmark either, so personally I might pay $100 for a somewhat working and otherwise nice 465. That is though, if I could personally inspect it beforehand, and ensure there were no obvious catastrophes waiting to be discovered. But on the other hand I do have some experience with troubleshooting electronics, plus a suitable collection of tools and test gear to throw at the problem.