New the site, new to the '2, cut me a break if I sound wet behind the ears.
So my 1993 SW20 3SGE (non turbo) that I've had for 8 months recently started making some funny noises and I'm not sure what's up so I figured I'd consult the vast wealth of intelligence that is the internet.
Firstly, during acceleration the engine has a rattle that sounds like marbles being sucked up a vacuum, really not sure where it's coming from but it only happens when the car is in gear.
Secondly, the engine smells like its burning oil even after short trips (15 min), but it isn't leaking. Do I need to replace the valve cover?
Thirdly, the engine is always cold and only heats up after long drives. I've found that when it's cold outside the engine makes more noise, and the other day when it was 38 degrees outside the engine sounded beautiful. Thermostat gone? And if so, is that a hard job.
I also wanna add that I replaced the spark plugs and did a compression test and found that 3 cylinders were running at 170psi and the 4th was 195. I have no idea why one was so much higher.
 
Cheers for any help guys, would be much appreciated

Firstly.  If you indicate where you are someone may be able to come take a look,   To replace the thermostat is not very difficult at all so long as you don't round the heads of nuts.  If your car has air con it can be a bit tricky.  Replace with a genuine Toyota thermostat only.  It will have its own rubber gasket.  Position the jiggle valve toward the top.    A correctly operating thermostat will have the temp gauge at just a needle width below half a gauge within five minutes or about two km of starting from cold.  Temp gauge will stay at that position continuously if cooling system is operating correctly.    The cooling system needs to be bled properly after this work is completed.  
 
High comp on one cylinder is possibly carbon build up in the combustion chamber and this is causing pinging in that cylinder which could be what the sound is that you describe as rattling.  Oil smell is more likely to be over fueling because of the bad thermostat
Difficult to diagnose without hearing all this stuff.
Come back with more info.
 

The temp gauge rarely gets near halfway unless its hot outside, most of the time its sitting a between cold and a quarter of the way up.
How would I address the carbon build up?
 
I'm located in Bayswater, Perth.
 
Thanks for the reply

Would it help if I took a video? I didn't originally because I don't think the quality will be good enough. Also it's hard to show the rattle because it's subtle and I'm pretty sure it only happens when the car is in gear.

Higher compression in one cylinder can be a sign of leaking oil into that chamber.