First Concern,
Mast is up, do I pull the pin to seat the mast?
Pull it, run 50 yards and dive.
The rigging seems to be slack, how do you tension the wires that hold the mast?
have one person pull on the shroud the other person puts the pin in a lower hole.Or better yet if you have the trap lines on, pull on them
The whole rig will tighten up when you pull up the jib
First, you want to put the forestay in the top hole of the chaimplate in the bridle. (With the mast up) if the shrouds are slack, then have one person hold one shroud, then the other person can remove the pin from the shroud chaimplate and move the shroud thimble down as far as possible and reinsert the pin. Then do it to the other one. That'll rake the mast as far back as possible.
If you have the shrouds in the bottom holes and it's still slack, then for now you'll just have to put the forestay in a lower hole. Don't worry, everything will tighten up when you raise and tension the jib, as the jib wire takes over the forestay's job once it's tensioned, and the forestay will go slack.
Thanks for the help, I'm a bit cautious not knowing what the heck I'm doing. Does it show? 
Also remember folks. Newer shrouds are shorter by two inches. They did this to induce mast rake.
Dont worry I learned this asking the same questions.
We all learn somewhere, thats what we are here for. 
Someone describe the "Mast Bearing" to me. It's not what I recognise as a bearing, lokks like a ball and socket to me. Am I missing a part?
Nope you got it, its a small piece of plastic that sits, between the mast and the mast base. It avoids the mast from drilling itself into the base and causing some serious damage.
Its a small piece of teflon, you put it into the mast base before stepping the mast. You can also use a penny, or another piece of plastic. I usually used pennies.
Shrouds and mast rake...
The position of the shroud in the side chain plate is dependant on the shroud length, main block system and the amount of mast rake you want. Typically more rake the better on a 16.
This will be trial and error on any boat as the size / height of the blocks vary, wires vary and frames vary (such as forward crossbar bend, striker tension). Adjust till the mainsheet blocks nearly touch when fully sheeted when sailing.
Adjust the shrouds. Tension the jib halyard to pull the rig forward and tight. Sheet the main, tight as you would for the days sailing. Look at the main blocks, the distance between the boom blocks and main ratchet set. Too much space? loosen the jib halyard... Move the shrouds down a notch or what ever... Tension the jib halyard again... Check the mainsheet tension and gap. Repeat if necessary.
If the main blocks touch, you will not be able to sheet correctly when sailing. Reverse the process and move the shrouds up a notch.
P.S. the forestay wire is only for rigging. It goes slack when the jib is tensioned. The forestay should not take ANY load while sailing. The jib luff wire should take the entire load. Otherwise the jib will bow off to leeward and upwind sailing will be more difficult. You can hold the wire with a small bungee so it doesn't slap the jib while sailing.
The pin is only for stepping the mast. You should remove it for sailing as the mast is supposed to rotate to orient itself better into the wind.