There can be differences between manufacturers as to which crystals to use. I have heard, for example, that dual conversion and ABCX receivers use different crystals for the same channel.
The best policy is to get a set of crystals from the manufacturer of your radio. Note, some transmitter crystals are buried in an RF module that plugs into the back of the transmitter. Changing crystals on those modules might work, but I have never done that. I think it could be risky, as in my many years of RC, the only time I have had to have something retuned was an Airtronics transmitter with a module. They do drift, and when they do, as in my case, the modulation was screwed up. It is a simple tuning tweak, but not something you or I could do at home.
Considering what you are flying and the fact that you will not likely be at the extreme of range, I would get get a crystal set, plug them in, do a ground range check, and fly. There are many other sources for crystals than Tower.
John