TPMS Sensor replacement question

Greetings experts ! I need to replace the tires on my 2008 Grand Caravan, SXT, 17" wheels, 4 liter engine. 115° F is a typical summer day temperature. Winter
lows are to about 25°. A pretty severe climate (edge of the Mojave Desert). Plan is to go with Michelin Defenders-90,000 mile tread. I drive about 12,000/year.
The tire shop tells me I should replace the TPMS sensor unit if I plan to keep the car for any length of time. Since I am only on my 3rd Caravan, the first being a 1984, I guess I qualify. I trade at 10-13 years. Problem is, the tire shop wants quite a bit for the sensors. The manager tells me if I get them myself, they will install them at no extra cost. I checked the internet Dodge parts dealers, who have substantially lower prices. The problem is, I don't know how much has to be replaced.
The illustrated parts breakdown shows: (First price is list price, second price is internet price)
1. To 1-22-07    Module low tire pressure, $46.70/37.36 1. From 1-23-07     Transponder, $51.45/41.16 2. Mounting bracket Left, $14.20/11.36 2. Mounting bracket Right, $9.10/7.28     3.Sensor Tire pressure, $72.25/57.80 3. TPMS sensor, $72.25/57.80 4. Hardware kit, $43.85/35.08     5. Cap, $12.70/10.16
Has anyone dealt with the TPMS sensor? How much of this do I really need to replace? Do I need 4 brackets, 4 hardware kits, & caps? What differentiates "Transponder", "Module low tire pressure", and "TMPS Sensor", or are they all the same thing depending on the model?
A different tire shop from the one I usually deal with tells me I only need a rebuild kit that consists of a couple of gaskets. My research tells me that the sensor batteries start going bad at 5 years, and most fail at 7 years. Therefore, replacing them now makes sense.
Your assistance is greatly appreciated. Thanks in advance.
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