The DIY thing applies to me unless I know that in the long run, it's gonna cost less and be a better job if I get a Mechanic to do it. I've seen firsthand the screw ups and extra time and money it costs for Mechanics to put right what a customer has done.
As for parts. This forum is a great resource with info like Buell turn signals, Ducati levers etc. I won't however go scouring every bike shop for a lower price because so far my dealer has been good.
I think, for their own good, at least in this area, Guzzi should do way more advertising. While kids are buying 600cc Japanese bikes that will do over 150mph, I think Guzzi should be marketing their 750 Breva as an entry level model. Do ads with kids on them etc. It seems a lot of kids are getting 600cc bikes as their first bikes so why not try to stylize some of Guzzis to appeal to them? Or make a concerted effort to go after the BMW customers?