Interesting! You were a "coxie" were ya? Now I have a pretty good picture of what you're really like! You're a TOUGHIE!
In the States we call you guys "cox'ns." Actually, there are quite a few different rowing terms, which I discovered the hard way. When we moved to B.C., we joined a rowing club there and were looking forward to rowing with the Canadians. On our first row, they put me in the stroke seat. I followed the commands of the cox'n, of course, but when he said, "Easy!" I began rowing easy, but noticed no one was following me. Everyone stopped rowing, for some strange reason. Who would have known that what he meant was "Way 'Nuff!"
5 ft. 100 pounds, eh? Yep, GREAT size for a cox'n!
Your trainer coached? PERFECT! Yep, definitely hire him. However, if you've coxed before, you've already pretty much got the rowing stroke down pat. You won't have any problems on the ERG. GO FOR IT!!! And don't forget that video I recommended; it's excellent. You can get it from "The Rower's Bookshelf" here in the States. If you can't find it online, let me know.
There's only one problem with the video: you really can't hear the cox'n's commands very well over the sound of the oars splashing through the water. But you'll LOVE rowing on the Charles; it's fabulous!
By the way, Alicia, you can find used ERGs for a lot less money than a new one. Rowers trade in their old ones for newer models. We sold our "C" model in order to buy the new "B." So check the bulletin board of your nearest rowing club -- or ask your trainer. Also, either U.S. Rowing or Concept II sponsors an indoor rowing championship twice a year, using all BRAND NEW ERGs, then, after the event, they offer those once-used ERGs at a huge discount. You might give that some thought. If this has some appeal for you, don't hesitate to contact them because they go fast.