My 2000 Mitsubishi Montero 4wd is having two issues as listed below. My knowledge about car's mechanical issues is poor so pardon me if I sound ignorant.

A little background: Head gasket was busted when I bought this car 8 months ago I got that fixed put new radiator and new timing belt and new battery. Put in new alternator 6 months ago.

1. Found oil in my radiator. I called the mechanic who fixed my head gasket when i bought this SUV, and lives in a different town (will call him Mechanic_A). He told it could be transmission fluid. But then I asked a local mechanic (Mechanic_B) who took a look at it and confirmed that it wasn't transmission fluid but oil. And transmission fluid looked good and no traces of water. Mech_B suggested a new radiator and coolant system flush. But then Mech_A said if it is oil in radiator then it could be some kind of stopleak or some gunk that previous owners had applied on heater core to prevent water leak into heater core and he suggested new radiator won't be required. I trusted mech_A and just got a coolant system flush and an oil change. However, oil came back into the radiator. I though I had to put in a new radiator. Advance auto parts guy said even with a new radiator your problem will come back because the issues could be with head gasket which is leaking oil into coolant system. Now I am not sure what to do with this issue as I cannot get a proper diagnosis of it. Also, I already have spent a lot of dollars on this and don't want to spend much more. Can i get an easy and less expensive fix on this. Your thoughts please?

I am not sure if 1st problem and the following problems are connected.

2.) My battery died last night got a jump start and got going but antilock light came on midway . At a red light the car wouldn't move normally after i accelerate as if the brakes were holding it from moving. Blinkers did not come on couple times and couple times they came on. Also felt like engine was running low like it was not running at its full potential. I managed to get home. I pulled the battery out and took it to autozone this morning the battery read low voltage and they will have to charge it before can give a verdict if battery is bad or good. Had put in a new aftermarket alternator in it about 6 months ago. not sure if I am having alternator problems again?