Car won't crank / start

What is your question?

MONDAY: Car started drove 20 miles then noticed temp guage showed cold plus warning light showed "Engine Hot - Turn Off A/C. (The a/c wasn't on & the check engine soon light wasn't on). Turned off car & checked under hood. No obvious leaks, steam, smoke, hissing...everything looked fine. Drove another 200 miles all seem ok. TUESDAY: Took to get computer checked for trouble codes...Nothing found but after they disconnected computer the temp gauge worked fine & warning light disappeared. WED: Car ran fine for 50 miles with no engine overheating THURSDAY: Ran fine for 30 miles then turned-off while driving & won't start / crank Local repairman (questionable competence) states the engine locked-up, water pump leaking & I will need overhaul/new engine. He also knows I'm not going to sink a lot of money into it & I think he is just wanting to get rid of me & charge me for diagnostic time