Not too relevant here, but on some engines it IS possible to change stem seals with the head in place. Supras for one. Not very easy, though, and if something goes wrong, the head will have to come out anyway...
it depends how competent you are with the tools, its hard to say whether you would find it easy, it involves taking off the head and removing the valves, valve springs, and then the seals themselves, fairly easy, if you're okay with removing and replacing the head, you shoud be fine, have you got a haynes?
yeah, its a different socket size, other than that you mayneed some decent long nose pliers or better still long nose molegrips, and you may need to buy a new valve spring compressor as the one most people use for an eight valve doesnt go deep enough in the head, other than that you should be fine. check the valve guides too though, by putting a valve in the head without the seal on and seeing how much side to sid play you have. most 1.4 and 1.6 16v engines had the same smoke problems you have and i think they were traced to slightly oversized guides, and you dont want to replace the seals and have it still smoke now do ya! also onetip, when you put the valves back in put a spot of grease on the end to avoid damaging the seal
Mine doesnt do that.....mine just smokes all the time...not a lot of smoke but it is all the time.....i have just checked my plugs and they are white at the end?.....will i need the engine rebored if the piston rings have gone