I know exactly what you speak off.
Here what I got from your message. I assume that you have 3EE motor in it. And it is typical for this milage to use up so much oil. And it will only get worse. If you had the car for the while then you might of noticed a slight loss of power and it will be dropping more. About timing belt, if you never changed that do it. (Timing belt has nothing to do with your oil and smoke problem about 50$ to 80$ garage will put it in for you for 350$) but change if you want to keep your engine alive. Moving on. It burns so much oil and smoking so hard because. Your piston rings are fried. And the head gasket is busted.(Head gasket is might not be at fault but ones you are down there change it any ways about 50$ at napa) And your cam shaft cover gasket will run you up about 20$ from Toyota dealership. If you want to rebuild your head go for it, but is not the cause of your smoke but it will improve your power. The main problem are the rings and worn out pistons and bores. Which calls for one thing. If you want to fix it as it is. You can just put new rings in and that's that, but that will only last you so much before it will start smoking again. If you want to go ahead and kill the problem for good there is a lot more involved.
-It pistons are not badly worn keep em` ( if you want to get new ones I am sure it won't do any harm)
-Rings must be new
-You will need to use hone on your bores to make then round again. (If don't know what I am talking about then take your block to a pro let them do it.
To put rings you will need a Ring Compressor it will run you about 80$ or less. Hone will go for about 50$ or less or more ( find some very dialed info on how to hone your block it has to be very precise). Replacement stones for the hone will be about 25$ per set of 3. I never gone as far as removing the pistons I can imagine you will be needing some kind of tool there as well. + the parts. You know what rebuilt 3EE motor will run about 500$ and to fix this out will about 400$ so think about it. I have the same motor as yours right now. It smoking and tripping like hell. That's why I am looking for the new one for the swap. I will never use 3EE again, it is junk. I suggest for your to move on as well

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P.S. To get rind of some or all smoke fast and cheap get it PCV valve it will be about 5$ and takes about 2 minutes to change. Then do a routine tun up
Wires - 60$
Plugs - 20$
Dist cap - 50$ and up
Rotor - 5$
Air filter - 20$ to 30$
Hope that helps. By they way the prices are in Canadian $ Good luck