Hi i have 2000 5.3 ltre v8 chevy tahoe oil in gas

Does oil pressure gauge work? If yes, what does it read.

Check the oil level. Is it normal, high or low?

Grab the end if the dipstick and pinch it between a thumb and finger, then rub together. Does it feel viscous like oil or thin and watery. Smell the oil... does it smell like gas or coolant?

Check the coolant level is normal or low?

Sounds like the wiring harness connection in the back of the speedo cluster is loose. This will cause crazy reading and the vehicle will perform like normal... sound about right??

Fuel injector problem , leaking fuel pressure regulator ,

Causes of gas in oil
On my 94 Chevy blazer, gas in the oil was caused by a ruptured diaphragm in the fuel pressure regulator that is attached to the fuel injector. Flooding the engine. An over abundance of gas in your cylinders will wash down your cylinder walls and accumulate in the oil pan.

Sure sounds like your head gasket is blown.

I prefer bosch plugs :

2000 Chevrolet Tahoe 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2000 Chevrolet Tahoe 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2001 Chevrolet Tahoe 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2001 Chevrolet Tahoe 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2002 Chevrolet Tahoe 5.3L 323CID V8 FLEX FI Z - GAP=0.040"; Original equipment is iridium. 2002 Chevrolet Tahoe 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2002 Chevrolet Tahoe 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2003 Chevrolet Tahoe 5.3L 323CID V8 FLEX FI Z - GAP=0.040"; Original equipment is iridium. 2003 Chevrolet Tahoe 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2003 Chevrolet Tahoe 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2004 Chevrolet Tahoe 5.3L 323CID V8 FLEX FI Z - GAP=0.040"; Original equipment is iridium. 2004 Chevrolet Tahoe 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2004 Chevrolet Tahoe 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2005 Chevrolet Tahoe LS 5.3L 323CID V8 FLEX FI Z - GAP=0.040"; Original equipment is iridium. 2005 Chevrolet Tahoe LS 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2005 Chevrolet Tahoe LS 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2005 Chevrolet Tahoe LT 5.3L 323CID V8 FLEX FI Z - GAP=0.040"; Original equipment is iridium. 2005 Chevrolet Tahoe LT 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2005 Chevrolet Tahoe Z71 5.3L 323CID V8 FLEX FI Z - GAP=0.040"; Original equipment is iridium. 2005 Chevrolet Tahoe Z71 5.3L 323CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe 5.3L 5328CC 325CID V8 FLEX FI Z L59 - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe 5.3L 325CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe LS 5.3L 5328CC 325CID V8 FLEX FI Z L59 - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe LS 5.3L 325CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe LS 4.8L 294CID V8 GAS FI V - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe LT 5.3L 5328CC 325CID V8 FLEX FI Z L59 - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe LT 5.3L 325CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe Z71 5.3L 5328CC 325CID V8 FLEX FI Z L59 - GAP=0.040"; Original equipment is iridium. 2006 Chevrolet Tahoe Z71 5.3L 325CID V8 GAS FI T - GAP=0.040"; Original equipment is iridium. 2007 Chevrolet Tahoe LS 4.8L 294CID V8 GAS FI C - GAP=0.040"; Original equipment is iridium. 2007 Chevrolet Tahoe LS 5.3L 5328CC 325CID V8 GAS FI J LY5 - GAP=0.040"; Original equipment is iridium. 2007 Chevrolet Tahoe LT 5.3L 5328CC 325CID V8 GAS FI J LY5 - GAP=0.040"; Original equipment is iridium. 2007 Chevrolet Tahoe LTZ 5.3L 5328CC 325CID V8 GAS FI J LY5 - GAP=0.040"; Original equipment is iridium

reason headlights got dim and eventually went off is because you drained the battery trying to start so first thing you need to do is charge battery after battery is fully charged check to see if it start if doesn't start pop hood and on fuel rail there should be a valve will look kinda like tire valve stem push in on that if gas sprays out then your getting fuel if it just dribbles out then you have no fuel pressure check fuel pump fuse and relay if both those check out good replace fuel pump
if you have fuel pressure then check to see if you have spark

there are gasoline vent tubes running on top the tank to the filler neck. check to see if the hoses are compromised in any way. these tubes also run to the front to a evap canister check these as well.

May be nothing more than a faulty gas cap or vent hose from the tank to the filler neck. Your charcoal canister for the fuel evaporation system may not be purging. It could be filling up with gas. It will eventually overflow, allowing you to see the problem.

You may have a fuel leak somewhere. Get it checked out ASAP!

bulbs or circuit board