Finishing my converted keg but need help deciding on equipment.

Ive got two kegs one is oversize in the middle the other is regular anheuser busch. Ive got one hole drilled in each and have only one set up with bulkhead, valve, diptube and mash screen. After brewing a few batches ive noticed I am in need of a sight glass. There are two websites Brewhardware.com and weldlessfittings.com that I will be buying it from.

Question:

It appears both sight glasses are the same from the two websites but my biggest hang up is the thermometer.

Do I buy $100.00 water proof thermometer use it for telling me my mash temp? OR

Do I just get the 2 inch or 6 inch dial thermometer?

Is there a difference in the blichmann thermometers or the "off brand"?

Please share experience with dial and digital thermometer.

I also have to appologize I wrote this really late at night didnt realize how tired I was.

Aplogies, but I really can't understand your question... Could you please rephrase it?

Sorry for the confusion I wrote this late last night half asleep. Main questions are:

Do I buy $100.00 water proof thermometer to use for my mash temp? Splash-Proof Super-Fast™ Thermapen™ http://thermoworks.com/products/thermapen/

Or do Do I just get the 2 inch or 6 inch Dial Thermometer? From Blichmann or brewhardware.

What is preferred from the general public.