Where is the thermostat
 

Is the thermostat at engine side of the upper or lower hose on the 97 Accord? Need to replace it.

If it's a 4-cyl, follow the lower hose over the transmission back towards the firewall. T-stat is sorta below the throttlebody.

Yeah, that looks like a pain to get to. Pulling off all that intake hose and lines looks to be no fun. Is there a gasket to replace with the thermostat?

Yes there is a gasket, more like an o-ring (at least on my 95 and older). It will "slip" around the outside of the t-stat. Of course, be sure to bleed the air out when refilling the coolant.

The big rubber intake hose isn't too difficult. The metal breather-tube just pulls out (maybe there's a hose clamp).

The bolts for the T-stat housing are a bit awkward, so a couple different extensions on your sockets.

A new thermostat should come with a gasket. It's a bit like an O-ring but it has a slit around the inside, so it fits over the outer edge of the T-stat & seals both sides. There should be a cut-out for the little rattle-pin of the thermostat, and a tab molded into the rubber gasket to force you to install it in the correct orientation.

Mine has an aftermarked radiator with no drain plug. Is there any problem with draining some coolant with the drain plug in the engine block?

I've never seen a radiator w/ a drain plug. Did you look carefully on the passenger side end?

Perhaps pull the lower radiator hose connection to the radiator to drain, or simply let coolant leak out when you open the thermostat housing. It will be diffciult to catch any of that loss, so you'll need at least 1/2 gallon of coolant to replace the loss.

good luck

Even with a drain, I haven't been fond of catching it & putting it back in. For the price of a bottle of antifreeze, just replace it.