They are pretty synonymous, although trip can be associated with pleasure or enjoyment. Connotation-wise, a journey is longer, and with a goal in mind. A trip connotates with vacation.

I don't have an answer because I am struggling with this myself, as I try to learn Spanish. The approach I am taking is to search for examples of spoken Spanish to listen to that are just at, or just slightly beyond my ability to understand. If there are subtitles or a written transcript, I try not to use them the first time because reading seems to be a crutch that develops my reading skill without developing my listening skill. I use recordings so that I can listen several times. Usually I will understand more at the second hearing, and even more at the third. I also force myself to listen to Spanish television programs even though I can't understand them. I don't know good resources English is; I've found "The News in Slow Spanish" to be so helpful that I'm willing to pay for it. I've heard somewhere that it helps to listen to a foreign language and repeat what you are hearing out loud at the same time as you listen. I sometimes do that, and I do think it helps me in some way that I can't put my finger on. Does it help me to listen? Possibly, because the task of repeating it means that I do not get enough time to mentally translate into English and therefore am forced to experience the language directly.