Yes mate not a bad shout, sounds like you know what you're doing. The 783 is the bus you want to Unirii, just outside arrivals door at airport, buy ticket before getting on bus as you can't buy on the bus - it was about 7/8 lei last time I used it, but as a taxi is only 30 lei (6 quid) I much prefer this as it's quicker and less hassle with luggage, BUT appreciate Blues on a quick stopover won't have a suitcase with them, so bus not a bad shout, BUT without air con you'll be sweltering mate.
From Muncii metro the ticket office is approx 10 min stroll, and gives you a chance to see where you need to be heading later that evening, so again good idea pal, enjoy !
For the metro go to kiosk inside station and ask for a 10 trip card (you get 10 separate trips for I think it's 12 lei (£2.50) ... so each time you re-enter metro it's classes as 1 trip... usually works out cheaper as you'll use up 2 trips getting to the ground for your tickets.