Since you'll be getting your tensioner piston in a compressed state, its a simple removal of the cap, sealing ring, and piston. Then put the new sealing ring on around the cap and place the piston in the cap the same way the old one came out. Screw the cap back in the head and thats it. Start the engine, let the clatter cease after 2 seconds, then hold the revs at 3,000 rpm for about 10-15 seconds.
Some tips - I made it easier for myself to remove the coils and place them on the rocker cover. Space is fairly limited on my E36 M42. I also disconnected the connector that plugs into the top of the A/C compressor. I would also use a long 1/2 inch drive breaker bar and then position it in a way that you can just sort crack the cap free. It may be difficult because it will try to slip off but you'll get it.