Welcome! This is indeed an exciting place to be
[You must be logged in to view images. Log in or Register.]
I'd say that generally there are more similarities than differences between Classic EQ and P99. Most noticeable differences are that on P99 you have item linking, Post-classic sky gfx, somewhat different resist mechanics, low level twinks with epics (immersion killer #1) and obviously different UI options (since the client is Titanium). You can "fix" this by using a custom downloadable Velious UI.
Since the server has run for over 5 years now the economy is somewhat off, but for a returning player this is not something you'll have to deal with. Still plenty of low level to find in the market which of course is found in the East Commonlands tunnel.