Hiya, just putting this out there. We were stuck on 1.7 for ages because I was "not in the mood", "too busy" to merge our customisations, then it occurred to me that maybe we don't even really use all of them.
Eventually made a test server with 1.10 and merged just the best and most valuable, rewrote as much as possible of them as plugins so future pain would be minimised etc.
So, I suggest checking first, see if your mods have been made into plugins already.
Then see if they are even in use.
Finally, if your Upwork plan fails, there's always http://osticket.com/customization