Toyota probably produces than anyone else on this planet, so this is due diligence , at least for the Nigerian interested in one

So, I'm bringing the first issue since I'm starting the thread.
After getting my own ELM Scanner , I put it to the test and saw a trouble code. It's reporting a bad crankshaft- camshaft correlation problem, should I be worried?

So after deciding to repent from my old "naija maintenance" ways, I've decided to purge my vehicle of all non toyota spec oil and fluids. The Toyota T-IV ATF should be replacing the Sea horse currently in the transmission (i know ), while the Toyota 5w30 will be replacing "whatever" 20w50 is sleeping in the oil pan.
I'm not too concerned about the transmission as Toyota recommends dexron 3 ATF in the absence of it's T-IV. Comments I've seen here about seahorse,which is dexron 3 itself, get me ? thinking occasionally though.

So I've converted to synthetic Engine oil and the engine still hasn't knocked yet. I've done over 400km of driving since friday , 4th sept.
However the parts dealer told me not to be in a hurry to change the seahorse ATF I'm currently on: Toyota transmissions are known to be one of the most rugged out there.
Sea horse is dexron 3 , the alternative specified by the manual in the absence of Toyota T-IV fluid.

Please gurus in the house what type of engine oil and transmission oil would you recommend for Toyota Rav4 1998 model?

Thanks i appreciate the info