****ek zaparkował [swój - not necessary, can be skipped] samochód i poszedł w krzaki siusiu. Gdy był zajęty, ukradłem mu samochód. Usłyszem "Don't you dare!" [Ani mi się waż!] ale było za późno. Zaparkowałem go z czterdzieści metrów dalej. Kiedy [gdy - both can be used] ****ek wrócił z krzaków, zobaczył/widział [wiedział = he knew] samochód, ale tylko odszedł naburmuszony [naburmuszony isn't the best word for "moody", but I can't find another at the moment].
Is a small electric golf buggy best described as samochód, or does that make it look as though I stole his BMW 5-series (whatver that means - I know nic about cars)?
I'm not sure, I'd rather say meleks (ukradłem jego meleksa), but I don't knwo if it's official in modern Polish [Melex was the name of the first company in Poland, about 20 years ago, manufacturing those electric cars you can see on golf courses and then the name, with polonized spelling "ks" instead of "x" became the name for those cars, but maybe now it's changed]
How do you park a car? - a valet comes and does it for you. Is this the kind of answer you were looking for? :)
How do you steal a car? - professional non-disclosure clause, I can't discuss it here.
What kind of grammar does a car require if you drive, park or steal one?jechać samochodem (Instrumental case - Narzędnik) - can mean both driver or passenger
kierować samochodem (Instrumental case - Narzędnik) or prowadzić samochód (Accusative case - Biernik) - those 2 verbs mean the driver only (so a passenger can jechać, but not kierować/prowadzić, unless s/he's a backseat driver)
zaparkować samochód (Accusative case - Biernik)
ukraść samochód (Accusative case - Biernik)
(in your example, however I wouldn't use the word "ukraść" it's too strong for the joking context. Maybe something colloquial like old-fashion "zwinąć", "zwędzić", "buchnąć" or more recent "podprowadzić", for example "podprowadziłem mu meleksa" instead of "ukradłem mu samochód", "mu" is a shortened Dative form [full form "jemu" = him] and we don't use possessive pronouns, like "jego", "swój", when it's not necessary, so in Polish "I stole his car" translates literally to "I stole him [the] car")