I'm considering purchasing a 911 and will be doing all of my own
repairs.  At what model series does this become unreasonable for the
home mechanic?  As a comparison, I presently have been successful with
all repairs major and minor to an '84 BMW 533i.

From what I've read, the later 964 series ('93 C2 or C4) sound most
appealing.  Can these models be diagnosed through standard procedures
(multimeters, various test guages), or does a $50,000 factory
diagnostic computer need to be hooked up to a diagnostic port?  993
series?  996? go back to the eighties!?

Thanks in advance for any advice.