I would also budget $30 to $50 for a second hand, high-end cassette deck if you don't already have one. An early to mid 80s brand name like Marantz, NAD or Luxman, with Dolby and chrome/metal tape settings. A separate hi fi component rather that one built in to a cheap boombox or whatever. That will give you the best possible analogue signal to digitise. And clean the heads after every ten hours of tape. You might also want to chuck in $10 for a tape head demagnetiser.

Only use Dolby where the tape has been recorded with Dolby.