Oil is pretty simple, as this is usually transported by oil tankers and not via pipelines, so can be bought everywhere where oil is exported. Therefore the timeline is plausible, you just need to secure the deals for that and that's about it. Gas is a bit more difficult as it relies heavily on pipelines and therefore will take more time, but the emphasis is on increasing LNG transport capacity (ships and terminals), to also become more flexible here.
Not really. You can read it as Baerbock stating the intented timeline and Lindner just reinforcing the point that a shutdown of the German economy without a replacement shouldn't happen. And Lindner's role is quite limited in this whole story as he is responsible for finances, more important are the Green ministers Baerbock (foreign affairs) and Habeck (economy). These two are travelling and trying to get Germany deals around the world.
Therefore I don't think the article is quite right in it's interpretation that a rift between FDP and Greens exist because of this topic. The far bigger rift is between Greens/FDP and SPD, as they differ on fundamental questions (do we deliver heavy weapons?). Greens and FDP have the same target here, just one is more cautious (the one who has to deal with the bills), which is quite natural I think.