Welcome
1) It will take as long as it takes to get your PPL. If you really remember everything, the hours you have in your logbook will count towards the minimum hours. The hours in the logbook you lost are gone. If you can track down the school or the instructor, you may be able to reconstruct the hours. But it is not a huge deal for your PPL, as you sound like you have over the minimum hours already.
2) You have NO CLUE as to how much you can sink into an abandoned airplane. Heck, you have NO CLUE as to how much you can sink into an perfectly flyable airplane that you buy. And, an abandoned airplane could have hidden issues that you don't find until you are well into the process. I HIGHLY suggest that if you want to buy an airplane, buy one that you can fly now. Then, as you fly it, you can fix things first, then upgrade to how you want it over time.
Some costs, assuming an airplane you can go places with. A very simple plane will be somewhat less:
Annual inspection, with NO REPAIRS - $2000
Engine overhaul - $30,000 and up. Assuming the major parts are OK. If crank, case and cam are bad - factory new for an O-320 (Cessna 172, Piper Cherokee 150) will start somewhere near $68,000
New Paint - $10,000 and up
New interior - $10,000 and up (top line interior can be $20,000)
Avionics - For glass cockpit and autopilot, figure starting around $75,000. This would to single GOC, ADS-B transponder, single display with engine instruments and autopilot. Assuming you can use one of the current nav/com as secondary.