2002 Toyota Camry Valve seal

I have a 2002 Camry xle V4 (very well kept and up to date with schedule maintenance). Slowly started making a noise (not loud but not heard before) the car sat- for about 4-5 days. Now, when I turned on the car he makes the noise and started smoking when started after it has sat. The smoke is white or some say light blue and it only last for a few seconds after I turned the car on so does the noise. I also notice my car feeling heavy and slow performing, little change in gas millage. I took the car to the dealer and after waiting 5 hours they stated "we don't know what’s wrong it maybe the valve seal but we need to let it cool" After 5 hours? I don't know about any recall or if there is an advisory out from Toyota of a smoke problem on start up on the 02 Camry’s but the mechanic has said it maybe the valve stem seals or valve guide seals but he has not actually looked at the vehicle completely to be sure (I guess still cooling) Can somebody please tell me why this maybe happening and what price or ball park range I may be looking at for this repair? Are there any other options for this repair.I really appreciate if you can assist me with these questions. My car is seating at the dealership and I can't sleep just thinking about what price tag they come on with.
My sincere thanks
Julie T