Hey everyone, this is my first time asking for help on this site, so forgive if my questions and problems are spaced out. I am the proud owner of a 1989 Volvo 240 which has been running strong for 2 years, but has been running poorly for the last week. No check engine light and no OBD codes have come up.

Symptoms
-The symptoms are mainly shaking/sputtering of the engine at idle and acceleration and loss of power. It sounds like my car might just stall out when I come to a stop or change rpm. I also noticed the engine oil dipstick and valve cover faintly smell like gasoline. I’ve been told this could be because of a stuck piston ring or clogged crankcase ventilation. I doubt this because the oil separator box was replaced and the rest of the pcv system was cleaned last year. Along with sea foam used in the fuel, oil, and vacuum hose before every oil change since I’ve owned it.

What I have done so far.
-Since my check engine light doesn't work, I checked the OBD-I port sockets 2 and 6, with engine off and key in run position, for any logged codes and came up with 1-1-1 on both twice (so no faults). Adjusted the throttle linkage correctly. Cleaned out the throttle body, which was filthy, I noticed that the intake manifold appeared wet. I believe this is because of a leaking fuel pressure regulator. I have also cleaned the MAF with MAF cleaner in hopes it would help. I have also listed the parts below I have ordered and will be replacing this weekend.
-new fuelinjectors
-new fuel pressure regulator
-new fuel pump relay
-new distributor cap and rotor
-new spark plugs and wires
-new engine oil and filter

What I suspect
-insufficent spark or no spark
-running rich
-fuel pressure regulator leaking gas into intake manifold
-leaking fuel injectors
-faulty fuel pump relay

The car will turn over and start, but I am reluctant to do so in fear of igniting fuel vapors in the oil.
What is the safest way to change the oil and filter in light of this? Should I bite the bullet and try warming up the engine before the change, or try draining the oil with engine cold (it's like 30 degrees F out here by the way) which will take awhile and might not get all of the oil out? Also do you think I am on the right track for fixing these issues?

Sorry for the long thread. Please let me know if you need more information to go on and I would welcome any advice to my problems