Newbie question

[Tom Mak]

Hi guys, I just picked up a 94 G20 with 126K miles.
Interior is in great shape while the outside got some
scratches, but the drivetrain is so-so.  My problem
with it is that the engine would make loud ticking
noises from the top of it even when it is idling,
running at any RPMs.  I am suspecting bad valves or
lifters in there.  What do you guys think?  This car
was sat for like a month or two.  My friend who also
has a G20 said that if you change the oil and do tune
ups. It might go away, the noise is caused by oil
stuck in the valves or something.  What do you guys
think?  Here is what I am going to change

PCV valve, Distributor Rotor and Cap, reset timing and
TPS, Fuel filter and the 2 drivebelts.  Spark plug and
wires and the air filter

Am I missing soemthing for tune up?  Or is that good
enough

And another question I have is the automatic
transmission.  I want to replace the fluid in it.
Infiniti of Scottsdale said there's a pan, gasket and
a filter.  I am going to replace all 3 of it and put
in some new redline fluid.  After I put in the redline
fluid, should I still machine flush the system, or
just drain it a few times and hopefully get all the
old gunk out?  Or should I machine flush it first,
then change the gasket and filter after and fill it up
with nice redline ATF fluid?

Thanks for the help
Tom