Never try to fix a Logitech product yourself as you lose the warranty. Just inform Logite and they will send you a new one, when its within their two years term of course. Their customer service is second to none.
I upgraded from a G25 to a G27 a couple of months ago. Although I miss the good old sequential shifter that came with the G25 the wheel is very silent at the start up and seems overall more smooth compared to the G27.
Like Paul said, its a no brainer if you wish to spend the money. When you are a regular racer purchase it. If you are a gamer that sometimes races but most of the times not, keep the DFGT.