Welcome!
That is one nice looking K. You will most likely find the maintenance issues easy enough to deal with, the info and friendship here is fantastic, guysd are great, from Australia to Scotland and everywhere in between.
I suspect if we were to list the items to go amiss it would be about 10 in number. Do a little research on these, none of them are difficult and the k in fact is very reliable. They are around so long its not so difficult to predict what goes and most things are easy. A Clymer manual is good too. All the info is up on this site but for me I prefer printed copy.
Fuel filter. [if bike is left sitting off road for a long time the stuff/rubbers etc inside the gas tank deteriorate and can block filter]. All inside the gas tank, if you are 6' 2" you might have big hands, small hands are a distinct advantage on this one.
Fuel pump can get destroyed with gunge too.
Plug leads [you already got that one]. K can be a small bit sensitive to plug condition so keep them good, they are not expensive. any misfiring check these and leads first.
Fuel lines: These perish, between the gas tank and injection rail. Moving tank around to access electrics does not help, replace them with longer but use BMW original, again not expensive.
Brakes: I see lots of posts to use braided grake lines.....also fluid needs changing every 2 years. ABS generally dies with age, most then run without it as it can be expensive to repair. Bike will run and stop fine without it.
Starter: Easy to remove and clean brushes/check brushes. However if fine maybe leave alone but its so easy its worth just doing as preventative measure.
Battery: When it goes wrong electrics can go funny. Before going at loads of stuff make sure its in good nick.
Head bearings: These make a big difference to handling. Did mine last Septermber and it was a great improvement. Although this can be a diy job doing mine involved complete dismantle of the head/stanchions/triple tree as the stanchions would not budge.
Electrics/earths, mostly under the gas tank. If you do have the gas tank off its worth cleaning these up but do them one at a time so you dont get things mixed up......
Rotors are not too bad to do, whether you keep to stainless or go to cast iron. You can buy new or used and some places in Europe will post over to you. Look up
www.motorworks.co.uk or motobins to name just two.
Plug leads ideally should always be original manufacturer.
Oil level. line uo with the red dot in the glass, bike on main stand. NEVER OVERFILL!!!.
Spline lube. You will see references to this. I have not done this and since my K is now written off I wont be doing it. This is not a diy for some, but can be neglected.
Once you get used to it you wil find you will spend more time with polish than tools, more time using than doing things and looking forward to the next long trip, sometimes inventing them or giving some minor thing a sense of importance to have an excuse to put some 5 or 600 miles up on it. They go for ever and there is not really anywhere to go after a K. There is nothing better.