Engine temperature higher on local?? Help!

Car: 2002 Impala, 3.4 V6 SFI, 92600miles

My car has a problem. Two months ago, I got the "Low coolant level". After I added some coolant, it was okay for 2 weeks. That message showed up again, and again I added some. Till now, I haven't gotten this message for more than 1 month. But new problem is: the engine temp is sometimes higher than the middle (especially on city with much traffic). It is okay when I drive on highway.

Just checked with a mechanic shop, it gives me an estimate (they said that there was a leakage problem). Could you please help me check which one is unnecessary?

Intake Manifold Set 77.63
VAL GSKT 21.55
Intake Manifold Gasket(Labor) 450.30
Coolant 16.00
Oil change,Lube&Filter 18.95
Environment Fee 2.00
Power Steering System Flush 89.99
Environment Fee 2.00
Transmission Flush & Fill 99.99
Environment Fee 6.00

Total:
Labor 669.23
Parts 115.18

Is the gasket problem serious? What's the function of it (why causing the heating problem???), Previously some guys told me that it might be the themostat or electrical fan problem.

ok well the UIM/LIM coolant leaks are very very common with the impalas, I had mine under a extended warrenty and got it fixed by the dealership, and the total bill was only like $500, so they ONLY replaced what was nessecary to fix it and didnt do all the other shit so they could charge themselves.

but looking at your list. this is what is bullshit and isnt needed....

power steering flush
tranny flush
environmental shit, buts its only $2 so it doesnt matter, they proly need to do it for regulations anyways.

but the gaskets and coolant of course are needed, and if there is a possibility of getting coolant in the oil, they have to chagne it (they didnt when they did mine, I was PISSED)

thats about as much of a help as I can be.

Thank you.

I found on the Internet that the newly designed gasket should be a metal one. But the guy in the shop told me the one they got was a plastic(rubber) one. I am afraid this does not solve the problem.

And generally, do they replace both the UIM/LIM together or can do just one thing?

THanks.

they do both since they are both common to go, but you can do just the UIM, but if you do the LIM you have to do the UIM. you have to remove the UIM to remove the LIM.

for those of you have just got completely confused...

UIM - upper intake manifold
LIM - lower intake manifold.

Thanks. Is there a metal one? And the bolts are required to be replaced at the same time?