Translation:We want to sleep a lot on Sunday.
What you have is a difference from one language to another between which prepositions are used in each language and even if one is used at all. So, sometimes you need to memorize one expression in one language for a different expression in another language. Spanish simply does not use the preposition on with days of the week, though English does. En can be translated as many different prepositions, because they use it in situations where we might choose a different preposition.
No, the infinitive is "querer". It is an example of a stem-changing verb. The e changes to ie if the stress is on that syllable. The stress is usually on the second to last syllable, so you have "yo quiero" but "nosotros queremos".