Upgrading radiator/oil cooler etc

Hi guys,

I own a 1992 GQ TB 4.2ltr automatic. I just did a big trip and noticed that the transmission was getting really hot. Fry an egg hot. I changed the oil before we left and it is still a nice reddish colour now. I am thinking about parking it up for a while and doing an overhaul on the cooling systems.
I bought the car only 4 months ago and it has just passed the 300,000km mark. I don't reckon the previous owner gave it any love, hence why i want to change a few things.

1: I want to install a new radiator, preferably an aluminium one. Also i reckon i should put in an oil cooler to deal with the auto fluid issue. Ive never bought (or installed) a new radiator and oil cooler and would like your advice/help. I was reading another post about having 2 oil coolers? Is this necessary? Where do they all fit? Where is the best place to buy one?

2: I am going to install a new water pump and thermostat. A friend advised me to put a thermostat in that opens at a lower temperature. What temp do the factory installed thermostats open at? Would you advise installing the same type or a different type?

3: Finally (sorry for all the questions), I have noticed a crack in my fan this morning. Are there any options, other than buy an exact replacement, for installing a better fan or different one.

Thanks to all.

Ollie