94' Intake Manifold gasket replace?

Hey guys!

My 1994 has been peroidically kicking up some white smoke and had a sweet burning smell when I have the air on (I think it just lets it in). So I took it to the shop a month ago and they replaced valves. It still happens so I took it back in and they told me now that I have to replace my Intake Manifold Gaskets. (I assume upper and lower since they quoted me for a set x 2)

Parts: $177
Labor: $257
Total = $478

This seems high but maybe I am wrong. Is this something I can do myself? How urgent is it? I drive about 600 miles every other weekend and really need my car....

Thanks for any help!

What valves did they replace?

if you got that upper plastic plenum,that's justice! if you got the mechanical ability you can do it yourself alot cheaper. i did one for afriend this past summer and i charged her $450. i did the upper and the lower intake gasket though. hopefully you dont need a new upper plenum. only problem was a plastic coolant pipe in the side of intake broke off. $4 part from dealer