As for the plugs, you dont need anything special other than a plug wrench. I always put some copper grease on the threads when I put plugs in, keeps them smooth and lets you get them back out again!

As for the filter, is it paper or metal mesh? Paper ones can be blown out with an air line, but usually just thrown in the bin and replaced. A mesh one can in theory be kept for life as long as its in good condition, and cleaning is part of this. K&N do their own cleaning kit, but is basically a de-greaser to get the grime off and a light oil to lube the mesh (not to thick now) so it filters the air better. You could improvise with brake cleaner.de greaser and a stout brush, just read the can first to make sure it wont rot rubber parts etc.

And have the book handy, just in case....

 

Every thingthat has been said so far is good ... One other thing that has been missed is ... With a new plug take off one of the lead's and put a new plug in then earth out the side of the plug ... Now you need to be carefull here ... Either get some good glove's or watch where you put you hand's ... Then just click the starter you should see a spark at the plug ... If you do all well and good ... If not try another lead ... If still no spark ... Six to four it's the HT lead from your coil than need's looking at ... Now why it happen's is a load of thing's ...
Too much oil in crank case ...
As all the thing's said above ...
Broken piston ring's ... A compreshion test will tell you if you have a doggey ring's ...
Valve guides are starting to leak ...
Or you some how have got oil in the petrol ...

Any way I hope that help's ...
John933