The 1971 series recently got an excellent Region 1 box-set from Discotek. Its opening episodes, directed by ex-puppet theatre director Masaaki Osumi, are surprisingly subtle, visually poetic, and generally well-written, dealing with themes more mature than most in the Lupin canon. After he got booted, Miyazaki and Takahata made this series their first experience doing TV anime; the resulting episodes can range in quality, but are a bundle of fun.
This is an excellent suggestion. I'd highly recommend starting with green jacket. The Discotek set is great, but if you wish to save a few pennies, I suggest waiting a month. Right Stuf will be selling a re-print of the Discotek set with new package art (but no extra features) at a discounted price point.
I also got into the series through watching the red jacket dubs, however I feel that the green jacket show is more consistently good. Don't let the first few episodes put you off. They are much more mature than some of the later ones. I still love them though and I think Dragoon explains them wonderfully.
If you want to watch something more up-to-date, I suggest the 2012 TV Special, Another Page. I was pleasantly surprised with how much I enjoyed this film and it quickly became one of my favourite Lupin features. Other recommendations from me are Plot of the Fuma Clan, Voyage to Danger and The Castle of Cagliostro (of course.)
As for Koike bLupin, I'm not sure on the DVD release. FUNimation picked up Fujiko in the US and Manga UK released it on DVD and Blu Ray in Europe (it was included on HMV shelves.) I am hoping this film will be dubbed by the FUNi cast, as I think they did a pretty solid job with Fujiko. It's likely, as Fujiko did seem to do well for them.
