On small engines (Motorcycle engines) the bikes idle and rev nicer when the engine is warm.
Be sure your choke is out until the engine is warm, and once it warms up, release the choke, and try it. It should work well.
If this simple procedure has no effect, clean your carburetor.
Buy a can of...
Yes you can, but shifting without a clutch and cause serious and expensive damage to your transmission.
It can grind gears, break teeth off of gears, and put excessive wear on your whole engine.
But to answer your question, Yes you can.
I think that is a fair price, as long as it is in great condition mechanically, and the body is in great condition.
Cars tend to hold their value pretty well, where as mini vans depriciate alot.
So I think that is a good deal for your car.