A friend of mine always had his serviced at the dealer, and after some miles, suddenly the transmission would not shift correctly and the dealer told him it's because some grit got into the trans and wanted a few grand to replace the trans... So how did the grit get into the trans in the first place? Good question for the dealer...
So I prefer to work on my cars whenever possible...there are some things that can't be done in your own garage, but still ..at least the oil change, etc... I can do...