It is of course personal opinion, but having travelled extensively with injuries as well as chronic limited use of one arm, I would spend the money. As I become older and hopefully somewhat wiser I realize when my comfort is worth some money.

I realize that it is frustrating not to be able to do something you could most likely manage if you were 100 percent, but in this case you may ultimately find the cost worth it. A few weeks ago for instance I paid a porter about $15 for assistance on Amtrak - I felt the need to indulge myself after a long exhausting week. It saved myself some physical pain and was well worth it.

Best of luck whatever you decide, but hopefully you will manage.