Translation:The trip had a positive effect on her.
I think so, but "voyage" is more precise, it's by air or by sea, so, as there is not context, "trip" seems better. http://www.wordreference.com/es/translation.asp?tranword=voyage.
Tuvo is the verb tener the préterito, tenía is in the imperfecto. As a non-native speaker I struggle with the difference sometimes. In this case (IMHO), the speaker is making it clear that to him/her, that trip has been completed. Tenía is also used in the context of habitual actions, similar to the english construction "I used to do something" Native speakers will often tell me that either form is good in many instances, but sometimes the meaning is changed...it makes it hard to figure out the rules. Goodluck!
My school in Chile taught me that pretérito is for a set number of occurrences (1 to many and would be explicit) and Imperfecto is for descriptions (was sad/beautiful, etc) or reoccurring (when I was young, when I went to school)... so if you're talking about a specific time it would be the first. If you are generalising about a period it will probably be the second.
That is a good rule of thumb. But like most things the actual use has fuzzy boundaries. Everything depends upon the intent of the speaker. The same story related under different circumstances may emphasize importance of a discrete period one time, and so the preterite is used Another time the events of that time are more important, that when is when the imperfect would be used.
the way i learned it was, preterit past(tuvo) would be the equivalent to a word ending in -ed and giving a set time and explicit ending. ex. "I walked my dog yesterday" while imperfect past(tenia) would be more like adding "was" to the sentence, and giving a general scope of time but leaving it "open ended" for lack of a better word. ex. "I was walking my dog yesterday when i got a phone call" I don't explicitly say it ended, it happened in the past but i don't have an explicit ending i was simply saying that it was going on, and i think that's the best way i can explain it. Now that's pretty much what other people on this thread have said, I just thought i would add specific examples and my own experience. i hope i helped at least a little bit.
Except., with the imperfect, one can say "I walked..", etc. http://www.trinity.edu/mstroud/grammar/pretform.htm http://www.speakshop.org/study-spanish/difference-between-preterit-and-