Transmission replacements are one of the most expensive car repair services. So, have a mechanic look under the hood and see if a full replacement is necessary.
Your friend wasn’t wrong to point out that the problem you’re experiencing is likely caused by the transmission, but that does not mean that you need to get the whole thing replaced. The problem could be something more minor, like a transmission fluid leak, which a mechanic can repair for you for about $300 to $400. Although that’s still a nice chunk of change, it sure beats the staggering cost of a full replacement.