Smokepole,
The vz. 36 was made until 1945, and the vz. 45 from 1946 - 1952, so if you can find a date (e.g., "47" on the trigger guard = 1947), that should settle it. Another difference is that all but the earliest vz 36's had a safety lever on the left hand side, whereas the vz 45 did not. The safety was largely unnecessary, since the pistol has a locking bar which could only be disengaged when the trigger was pulled. Supposedly, there are other minor changes, mostly enacted to make manufacturing less expensive. Also, a vz 36 will have a "CESKA ZBROJOVKA AKC. SPOL. V PRAZE" slide marking, while a vz 45 will say "CESKA ZBROJOVKA - NARODNI PODNIK STRAKONICE" or "CESKA ZBROJOVKA - PRAHA" so look for the hyphen. A vz 45 can be further narrowed down by whether it has a "MADE IN CZECHOSLOVAKIA" stamp, which started in 1948.
With regard to value, the vz 36 is a lot less common than the vz 45 (I'm still in the process of translating a reference, but my initial perusal suggests that 95,000-200,000 vz 45's were made, while fewer than 30,000 vz 36's were made. I've never seen a vz 36 for sale, but a vz 45 in the US (unimportable now) will fetch $175+ in beat condition, $300 in 95%+ excellent condition, and $450-$500 new in box (though Marstar in Canada used to have them for $100 and change... whereas in the US, we are paying a premium for a fixed supply of old imports).