Depends on what the problem is. One warning I can provide. Use only genuine Honda ATF fluid in your Accord. The use of any other fluid will cause problems. I suggest you seek out a professional to...
If it were my car i would replace the transmission. A website www.car-part.com gives you a list of used parts all over the country. If you are a do-it-yourself-er it is the cheapest way to go....
If automatic, change fluid and filter. If manual, need clutch, pressure plate and throw out bearing. If none of these work then, you are in for a real treat moneywise.
If it is an aluminum or steel deck 215 that has shaft drive- it was designed to remain sealed for the life of the unit. That said, you can pull the trans and split the case, clean it out and refill...