As TheTrisagion says you're fine so long as you don't go to take Communion, or behind the altar. Be sure to ask your priest for any other big (or small) no-nos but those should be two of the biggest ones.
Really, sitting back and observing the service will help you to understand it more and more (pay attention to the hymns that are sung and check the church calendar before/after the service, and things will fall into place faster but this still takes weeks), and don't be afraid to ask about things you don't know or understand. There's nothing wrong with lighting candles or venerating the icons though, so don't worry there. Indeed when I was a catechumen I'd wander around the church after the service and take time to look at the icons and read about the lives of the saints once I got home.
Same with crossing yourself (oh this is a good one to learn - the whens of it). As an example, at our parish people usually cross themselves at the "Glory to the Father...", at each line of the Trisagion Hymn ("Holy God, Holy Mighty, Holy Immortal have mercy on us), after the Lord's Prayer, whenever Alleluia is said thrice ("Alleluia, alleluia, alleluia, glory to thee o Lord"), and at some prayers to the Theotokos. Usually we bow when the preist blesses the entire congregation, and also when the deacon faces us whilst censing. Oh also, when he says "Oh Lord, save the pious / And hear us". The other thing you could do is take note of and find out some of the customs that are done at your parish and learn those (and I imagine speaking to parishioners about things you take note of would be very helpful here). This kind of stuff can take a while to learn though.
Also, perhaps some books focusing on the Liturgy might help to "acclimate" you. Your parish should have some (or at least the text of the Liturgy itself) but if not you could look at Meditations on the Divine Liturgy, by Nikolai Gogol, which has each portion of the Liturgy and a short explanation of it immediately afterwards. Such texts could be really helpful.
Best wishes, wherever your path may lead.