hazards are a simple diagnostic. do the indicators work fine when used normally, if so then the base circuit is then fine and the fault is from the hazard switch to the hazard relay. if the noise is from under the dash try and see if it is possible to touch the relay while operating the switch. swap the relay for a new one this normally solves all the problems. the other option is cleaning the contacts on the hazard switch etc as corrosion might be causing a problem.
Oil pressure i would have thought to be similar to your xj. as above give the engine a flush through with a cleaning agent and replace the oil with the correct viscosity and a new filter. then check the pressure gauge again. these guages either work forever or fail straight away as they are not 100% reliable and are suspect to heat breakdown from the engine. the downside is that there is no other pressure sender that fits the jeep engine apart from the jeep made type. the only way of fitting another is to make an adaptor from the jeep thread to the replacement you want to fit. not looked into it fully myself but one of the things on my to do list.
with the heater not working look in the engine bay and you should see two hoses going through the middle of the bulkhead/firewall. run the engine untill warm. check the radiator top hose for warmth then go to the hoses previously found and touch them, they should be warm as well or at least one, if there is still no heat then you might have an air lock in the system or a blocked heater matrix and the heater matrix will need to be flushed through and the system vented of air.
