If you're able to replace the head gaskets on your engine yourself then it can be worth it if you plan to keep the vehicle.
The cost to replace the head gaskets yourself is around $50.00 to $100.00 in parts if you buy the parts online and if you have the tools to do the job.
I've replaced the head gaskets on my 1993 Chevy Van with the same engine as your Suburban and I got the head gasket kit for $41.00 on Ebay.
The head gaskets came with the valve cover gaskets, exhaust manifold gaskets, intake manifold gaskets, throttle body gasket etc.
You can reuse the head gasket bolts but make sure you torque the head bolts down properly and it's a pretty easy job.
However you have to remove the heads and everything else to get to the heads and then replace it.
It took me 2 weeks to fully put everything back together because it was my first time doing the head gaskets and I also had another job to go to.
I worked evenings and weekends on it.
I worked some while I was waiting for the parts such as tearing it all down and cleaning it up and then within another week I had everything back together.
You also need to make sure you adjust the rockers for the valves so they work properly.
And you need to set the timing again.
But for around $50.00 in parts and your time it can be worth it to replace the head gaskets.
I was quoted $1,000.00 for a shop to do the job which was pretty decent for all the work.
But if you need to pay a shop you can go online and buy a rebuilt Chevy 350 crate engine for a little more money and then just remove the old engine and put the new one in place.