Caliber,

Beware CETME's by Century. I have one and it is fine, but I know some owners who haven't been so lucky. IE: headspacing is set piss poor, extractors springs are weak, etc. Parts are cheap though.

Most, but not all parts, are interchangeable. Go to http://www.cetmerifles.com/forum/index.php
and get the full skinny. I put a HK wide forearm stock on mine and it took a little "modifying".

HK mags don't work in mine, the mag catch is not the same (?), the mag doesn't insert fully, and the bolt can't capture the rim of the round. Might be just mine, I dunno.

If Marlin sells you his for that price (which is good, the typical price is $400 +), better than one sight unseen and not inspected. Just my 2 cents.