There's no point in spending a bunch of money to go from 53/39 to 52/36. You get about the same low gear using an 11/30 cassette with maybe no other changes.
On the high side you are 3 or 4 gears above Eddy Merckx in any case, and you are not him.

Contrary to JohnDThompson the crank and bottom bracket could stay and replace only the spider/PM.

I suggest leaving the front and using an 11/36 cassette, with a long cage RD that will run it. That and a longer chain will get about 28 gear inches, down from the 36 G.I. that you have now.

That , or HTFU, I guess, but when I was in that situation, I changed to 48/34 withe the smaller spider, later adding the spider PM. Ran that with 11/28 for quite a while, but now have devolved to an 11/34, for a 1:1 (26GI) low gear.