You (or the mechanic you use) shouldn't have to remove the intake plenum to change stem seals unless it's modified. Get a tube of RTV (Permatex Ultra Grey unless you like Toyota's FIPG). Ultra Black and Ultra Copper work too.
You should reseal the semi-circular plugs and the distributor plug behind the coils. make sure the surfaces and clean and dry, because RTV doesn't stick well to oily surfaces unless you're using Permatex Ultra Blue. But I'd still clean them well.
Do you have the lever type spring compressor? I prefer the rope trick to hold the valves in case of power failure with an air compressor. Here are related discussions and similar DIYs below. If needed, you can also PM ToyotaPartsMan, he's a dealer parts manager in Newman Georgia and gives members 30% of msrp. Otherwise use Fel-Pro from local parts stores or rockauto.com.
While at it might as well check the valve clearances or even do a complete timing belt job. Borrow the large socket and a torque wrench from Autozone's free loaner program (with refundable deposit) if you don't already own them. Of course a decent mechanic should already have these. The shop may charge 5-6 hours of time if this includes the complete timing job using the following parts.
An example of a complete timing belt job can include:
GATES K030295 Micro-V AT Power Steering Belt $5.14
GATES K050435 Micro-V AT Alt/AC Belt $14.10
FEL-PRO TCS45920 Crankshaft Front Seal Set $5.10
FEL-PRO TCS45641 Camshaft Front Seal $3.66
NATIONAL 221820 Polyacrylate Oil Pump Shaft Seal $2.86
GATES TCK199 (1 Belt, 1 Tensioner, 1 Idler) Timing Belt Component Kit
STANT 48278 180° w/Jiggle Pin OE Type Thermostat $10.94
AISIN WPT010A Water pump w/o housing $30.79
FEL-PRO VS50304R1 Valve Cover Gasket Set w/Spark plug tube seals
Shipping about $20
You can add NGK wires and Iridium-IX spark plugs and radiator hoses too. etc etc