Ford does not specify a manual transmission fluid change except when used for towing or other harsh service. Under those conditions Ford recommends a change at 60,000 miles. That's the official Ford line.
In real life, it is a very good idea to ignore what Ford says and change the manual tranmission fluid. Of course, changing a manual transmission's fluid is less important than for an automatic transmission, but it is still a good idea.
To check the level, you must find the oil fill plug. You then remove it and see if the fluid level is within 5 - 10 mm of the fill plug hole. Of course this needs to be done on a level surface.
It is not too late to change it and there is absolutely no need to "slowly" change it. Many people find the shifting improved when they change to fresh, premium manual transmission lubricant. I have no personal experience with manual Focus transmissions; however, I am sure others will be happy to post their recommendations for manual transmission lubricants. On BMWs I have heard many good things about Red Line MTL, but offhand do not know if it is appropriate for the Focus transmission.
One piece of advice. Take the fill plug out before the drain plug. Not only will it drain better, but if you find you cannot get the fill plug out, you will still have a tranmission with fluid in it! Not much worse tran draining the fluid and finding you cannot refill it due to a seized plug.
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