Would it be better to make a gasket or use RTV sealant?

Make one, let it overhang a little where you can later go around it with a razorblade when it's all tightened up. Also use some gasket sealent since you are making it out of gasket paper. That gasket paper isn't the best stuff around.. Try to find an actual gasket that will fit IMO.
 
Well you have to pull the timing covers to get the crank through it, so I would imagine that installing the seals would be the last thing to do.

Leave the covers and seals out, and do it last.
scott