Depending on where you are driving to in Croatia, you might need to buy the vignette for Slovenian Motorways, but if you are just crossing from Trieste to Reijeka there are a couple of roads where Vignette is not needed.
You can buy set of bulbs (H2,H3,H7...) in Hornbach or in Coop bau und garten. Consider to throw in one towing rope, Croatian cops ask me for one last year (when they didn't find any other issues) but again maybe that was 'cos I'm Serbian and generally our nations still have some issues. Exchange some eur/chf to Kuna's because lots of gas stations and stores (further from highway) won't accept franks not sure about euros, but there are exchange point in almost every village. Good luck with your trip, hope you'll enjoy it, it's a beautiful country. Cheers
Last month I drove from Venice to Slovenia. If you do intend to use the motorway to cross Slovenia don't forget to buy a Vignette . You can buy them from the last few service stations in Italy. They cost 15€ for a week or 30€ for a month. Don't risk it, I saw 4 or 5 random police checks in the 2 days of motorway driving I had there.
But the motorways are great, not too busy and the drivers were careful and considerate (apart from a few Swiss boy racers with AG plates on the way back on Sunday). And everyone was very friendly and spoke great English.
Slovenija is small, motorways are sparse and actually not evey A and B can be reached through them, depending on where you enter and exit, you might better opt for country-side roads to see some scenery/attractions and save at least 30 Eur - assuming you will drive back at some point. The time difference will be insignificant(the country is small).
To cross Italy you will need some 40 Eur one way in tolls, in a good weather motorways are way faster, in a bad weather country-side roads might be faster - too many incidents last time I drove in heavy rain. Be carefull - 130 Km/h limit is for foreigners, you will be tail-gated in the left lane at this speed and eventually overtook from the right, so use the left lane rare.