Traduko - Rumana-Hispana - Doresc să cumpăr această maşină dacă oferta mai...

As it is in Romanian, but maybe in Spanish it is better to have the verbs at conditional:

Deseo comprar este coche si la oferta sigue siendo en pie. Por favor comuniqueme su dirección y cuando está dispuesto a realisar la transacción.

You're right that in Romanian it is in present indicative, but it sounds more polite with the conditional. I hesitated between "dirección" and "domicilio", but chose the latter. Either one would work. There are a couple of small errors in your translation, though: it's not "siendo" but "estando", since the phrase is "estar en pie". There is also an accent missing in "comuníqueme" and it's "realizar" and not "realisar".

OK, thanks for the information! My Spanish is not flawless since I am not a native, anyway, it's always good to refresh your knowledge(hehe, "estar en pie" was logical, but I guided more after what sounds better, big mistake ) and to learn new things also!

p.s. It's not my translation that needs to be validated.