If it was me I would drop the oil pan and see if there is gunk in the pan. Possibly the screen on the oil pump is clogged and after sitting for a while the junk settled to the bottom. So, drop the oil pan clean it of any gunk you fine and see what happens.

And the prices don't seem that High. When replacing a raditor it is typical to replace the hoses and other such things. What did those estimates include it is probably more than labor. <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />