Curved Greenish yellow band across the bottom of picture.

Yes, both amps need to be replaced. Typically when an amp fails it greatly stresses the other amp. So it's HIGHLY recommended that both are replaced for greater reliability.
The only advantage of replacing the 110's with 150's or 180's is a higher amperage rating. (Able to withstand a greater current draw with less stress) But the circuit is designed with the 110's to operate efficiently. If the supplier doesn't have the 110's in stock you can go higher with no problems.
Unless you have better than a basic understanding of electronics I wouldn't attempt the repair yourself. These amps are about half the dimension of a pack of cigarettes with multiple pins protruding from the bottom. These pin fit into the slotted holes in the board and are soldered in from the underside. That means you have to remove the board they sit on and de-solder the amps that are in there in order to install the new ones. It can be a bit difficult and bending the pins happens even to the best of techs. It's what you do or don't do to remedy the many problems you could encounter.
How much does a typical service call cost... Well, it would depend on the area and how far the tech needs to go to make the call... But a service -call won't fix this set normally. I know it's a buggar but it will most likely have to go to the shop. Some techs simply remove the board and take it in for repair - then come back to install it. But that leaves the tech with only static testing and if there is anything more wrong it's a back and forth game to the shop for parts, tools etc... Ask the shop what they do for this type of repair. You can explain what you believe is wrong and ask what they typically charge for such a service.. They should easily be able to give you a ballpark... In my area I pick up the DLP and PTV's just because I like to be precise in my repairs. Guess I'm a bit anal that way but I have very few call-backs. Shop install on those amps we charge $425.00 parts, labor, tax, p/u and del.
You could cut your p/u and delivery charge by taking the unit in yourself.
Lastly, PH001 and 002 location numbers where you'll find in this case the connector pins for the digital module. Everything on the board has a location number C338 is a capacitor located in the 300 series of a particular circuit. D955 is a diode in the 900 series and so forth.. PH is a connector and at 001 and 002 you'll see a connector and on the underside the pins of that connector are soldered to the board. In this case look at them carefully, you may need to re-flow some solder on them to eliminate ringcracks.
If you don't do the job pass it along to your tech to have him look at these soldered connectors for reliability issues.
Good Luck!
Bill

The problem sounds like convergence amps have failed but without the model number I can't really tell you what STK number they are... If you want to reply with the model number I'll look up the schematics for it and let you know.
Bill