Do you still have the engine out of the boat?
If so, I'd say that this is certainly the right time. Getting access to the packing nuts is really a pain in our boats - you can see them, you can reach in and touch them, but getting a wrench on them and rotating is difficult.
It's not really a huge job even with the engine and trans in place. Drop the partitions next to the engine, lay down, loosen the jam nut and unscrew the packing nut. Use a dental pick or something similar to pull all the old packing out, put in the GFO
packing from SkiDim, put things back together loosely. Wait till you get to the lake, tighten up until you have a good drip rate (be generous at this point), run for awhile, retighten. After ten hours, check and re-adjust to final drip rate. Good instruction here
. It'll be a three or four hour job the first time you do it, less than an hour the second time.
Remember that you'll have to re-align the propshaft when the engine goes back in; leaving the packing loose will make that a bit easier.