(1) Just degrease, gurney, prime and paint is good enough for an engine IMHO. Just make sure you use some high temp stuff for engines otherwise it might blister. TBH I would leave the alloy gearbox as alloy and not paint it. It's up to you but no doubt if you do the same as for the block it should turn out half decent.
(2) Clean both mating surfaces to get them perfect. Use a smooth file to make sure each surface is flat (just used to clean off the yuckky bits). Use a new gasket and some permatex no 3 on the gasket. (Metho gets permatex off). I did this recently - I spent 2 hours prepping the mating surfaces and have been rewarded with no leaks. Make sure the timing chain cover is flat! Do not ditch the gasket and just use goo.
A new gasket will set you back about $3.75 and a bottle of permatex no 3 about $6.50. Also get your self some locktite 262 Stud lock to put on the crank pulley bolt - that way you don't need a lock washer - torque it up to 70ft/lb's. Make sure that you slide the crank pully on BEFORE you do up any of the timing cover bolts. It would also be worth replacing the cover seal that the pully fits through, you don't want to have to pull it all apart again.
Dave (sitnlo62) told me what I have just posted there and he was totally right.

I followed his instructions and as I said, have no oil leak from the timing cover anymore.
(3) I would only paint the outside of the caliper. Mask off the innards (especially the pistons). You can't be too careful when it comes to brakes IMHO. It probably won't make a difference but if it does, you are putting your life and others at risk
