$15 bucks for a good one was probably about right, the old Black line was probably Dacron used primaryly back in the 50's and 60's and its still popular by a few today.  35 lb test was an ok choice to learn with if it is of good quality,,,some poor quality lines will drive you nuts and you'll think that its the reel and you'll never learn to cast and give up on level winds.  Tips on how to cast a level wind are all over the net,,,probably even a few videos on U tube,,,Just put on 2 to 6 ozs of lead,,go to an empty ball field and start slinging and learn to use some thumb pressure to control your casts. Play with the side plate bearing (left side plate cap) to adjust the pressure on the axle for control of different weights.  In a couple hours you'll be an ol pro in no time at all 

Need to pour some water on the spool to keep the line wet while dry casting . Keep doing it and you won't have a thumb print left...You will really need to do that if you are using braided line....

The nut on the left of the axil aplies various degrees of tension to the spool axil that restricts the free spool effect...it helps to control the cast and you should eventually come up with a pretty standard amount of weight that you intend to be casting(sinker+bait)and therefor be able to set this at one tension that works for you...
Price varies as to condition of reel and frame of mind of seller...when you consider the cost of modern baitcast reels...you did well on your purchase...
Backing on a spool had/has many reasons(the newer spools dont have a line stud on the spool and with the newer teflon coated braided lines..no backing=slipping)
Line recomendation on newer reels(this primarilly aplies to spinning)is determined by capacity
(yards)as the older spools were deeper than the newer ones..it was explained to me that they concluded that you couldn't effectively cast when the line got down below a certain level anyway so why have the spools so deep...but,I replied, what do you do when a 50lb cat runs
and you only have 80 yds of line !
The same person at the Penn site told me that the  Penn spinning reel that recomends 30lb mono
(he was talking about the Penn Captiva cv6000)also suggest 50lb braided...
20-40 dacro is good for a 109