My Mitsubishi Magna v6, 2003 model has an oil leak and I was told by the mechanic it is the rocker cover gaskets that need replacing. This was going to cost me $450 which I don't have at the moment.

That does seem pretty steep. Although it is a fairly simple task in many cars, particularly 4 cylinder, With V6 there tends to be many components that must be removed before valve covers can be taken off. From what I can find out, the intake manifold must be removed-thank you engineering- and that is the major cost. May be a DIY job but fairly complex.