Once she's all bolted back, go round and double-check that you haven't forgotten anything (including water and oil - it's surprisingly easy to do
). Before you put the plug leads back on, and preferably with the plugs out, crank her over for a few seconds until the oil light goes out to prime the new filter. This should also give the fuel pump a good chance to refill the float chambers.
Then fit plugs and leads and flick the switch. Do
not forget to re-torque the head bolts once she's been warmed up. It's generally recommended to do this while the engine is still warm on cast-iron heads but you have to remove the rocker shaft to get at some of the studs on these, and you need to set the valve clearances when cold, so that's a PITA. As long as you
do re-torque them (to allow for the gasket compressing as it heats up) it's fine doing it once it's cooled down again.
When re-torquing don't just apply torque wrench and pull - you'll probably end up over-torquing some of them. The correct method is to
undo each stud about 1/4 turn then re-tighten according to the normal tightening sequence (no need to slacken them all at once - slacken and immediately tighten each one in turn)