Have a google for lifetime bmw maintenance schedule, lots of good guidance for intervals there. You shouldn't need to do the plugs if you had a proper insp 2. Unless you've done 7/8k since then I wouldn't bother with an oil change either. I don't run anything over 10k but aim for 7.5 or 1 year whichever comes first.
I exclusively use MANN for filters (one of the OEMs for BMW) and Petronas for engine oil.
Your box probably won't have been done so that may be worth doing before winter, defo before your trip. I tend to inspect air filter and only change when it looks grubby, every 18 months or so. Cabin filter is usually annually along with an air con cleaning bomb.
If you really want to get into DIY servicing, get a socket set (Halfords are not bad for their sets) and a decent jack and axle stands. Ramps are worth considering or a portable lift if you have the space and cash.
Plugs and filters are worth keeping in stock as you can get them cheap when carparts4less have a sale on.