You should be fine - as has been said, the first few frames will be exposed, but oh well. The film tends to stay pretty tightly wound around the spool, so it shouldn't be too bad ...

The only thing I would reccomend is that you remember to close the "exposed" tape on the end of the roll after exposing the whole thing. I've fogged half a roll by forgetting to to close the tape and having the roll unroll itself.

have fun with your foray into medium format ...