Lower intake manifold gaskets are known coolant leak points on the 3100 & 3400 engine. This sometimes presents with coolant in the oil but more often it's just an external leak under the throttle body near the coolant temp sensor and or behind the power steering pump. Basically right where you circled it.
It's worth mentioning that head gaskets are also known failure points on this engine series. Once you lift off the lower intake manifold you're most of the way to head gasket R&R job. The cylinder 6 misfire could indicate a head gasket or just an intake manifold problem on #6. Investigation would be prudent.
Fel-Pro likely has a set that includes the valve contains most of the gaskets from the lower intake to the tippy top of the engine. Make sure they include the valve cover gaskets and the throttle body gasket.
Be bloody careful of the brittle plastic parts (hose barbs, electrical connectors, etc) as you disassemble the car. Otherwise you'll get to go salvage yard picking for the jiggly bits you broke.
Upper and Lower intake manifold gaskets are a fairly straightforward R&R job. One gotcha is the pushrods are weaved through the lower intake gaskets.
If you're a complete newbie to wrenching sit down and watch a youtube video or two and decide whether you want to jump into the deep end of the pool.
If you decide to go for it, get a service manual so you have the torque specs and sequences for stuff like the head bolts. The Haynes manual would do fine for this job as it's mostly mechanical.
Rainman Rays' channel on Youtube has a fairly decent intake video series on a leaky 3500 engine in a Saturn that should be similar to the 3400. Thankfully GM used aluminum alloy intakes on this engine series and not the plastic fantastic intakes like they used on the LS4 & 3.6L.
Stripping it down to the heads.
Reassembly.
