Maintenance schedule, 2000 Solara

I have a 2000 Solara, V6, manual transmission, second owner, 43,000 miles. I bought the car at 4 yr/28000 miles. Previous owner changed
the oil every 6 months. No other maintenance done. I had the vehicle inspected by the dealer at purchase and replaced a CV boot.
I change the oil every 6 months/<50,000 miles. I waited 10 months this time and the oil color on the dipstick is still gold, darker than fresh out of the bottle, but not black or even brown. Also changed the air filter about 9 months ago.
I skipped the maintenance by the dealer at 30,000 mile because the coolant fluid looked nice light red, and the transmission is manual. On the coolant, I'm looking at it in the reservoir though as there's no fill cap on the radiator. Is there sufficient mixing of the coolant from the radiator to the reservoir to use the reservoir as an indicator? The coolant looks a little darker now in the reservoir, I think.
At 6.5 yr/43,000 miles, I'm thinking I should have the dealer do the 30,000 mile maintenance :-). I know, should have just done it at 30,000.
Question: Can the timing belt and spark plugs wait? I've exceeded the time but not miles for those. Manual says 4 yr/60,000 miles for both. Is a timing belt inspection easy to do, or is it difficult even to get a look at it? I'm thinking of asking the dealer to inspect it and replace if necessary.
Paul S.
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