Blue smoke means your engine is burning oil. hence oil leak. The only way to make sure that your turbo is pushing oil from the exhaust end is to loosen the nuts that link the exhaust pipe to the exhaust end of the turbo, start the engine, rev it for a while and check if the loosened joint is leaking oil. Toyota estimas use CT9 turbo chargers or can be upgraded to CT12A which fits perfectly. You can get refurbished turbo chargers from gumtree sometimes for as low as 50 pounds. You can even fix it yourself if you got the heart. Am no mechanic but I replaced mine myself. I downloaded some videos on turbo charger replacement from you tube studied them and when I was ready, I fixed it and I have no problems at all. Its a messy job coz of oil and water but its manageable and fun.