Low Testosterone

I have just been diagnosed with Low Testosterone.  I am 53, 6-2", 195 lbs, and in overall good health.  I have high b/p (controlled with meds) and high lipids (also contolled with meds).  My Testosterone levels were:

total serum testosterone  269 ng/dl
free testosterone  5.9 pg/ml
and also tested
prolactin   5.1 ng/ml
TSH  0.98 ulU/ml (?)

I kinda expected the dx, but was still taken aback and didn't ask any questions.

Doc started me on Testosterone Replacement Therepy (TRT) via injections.  Didn't ask specific type, but did overhear that it was 200 mg.

My issues/questions are - just how low is my testosterone?  what can/should I expect from TRT?  When should I notice effect?Physical changes?  

I go back for my next shot in 3 weeks.