Can you tell me where you read that knee replacement for a valgus knee is more difficult?
I don't think you need to worry about that because, although it may involve re-balancing of some of your knee ligaments, that is often done during a knee replacement anyway.
There are three compartments to your nee - lateral (outer), medial (middle) , and patello-femoral.
Having a valgus knee is less common than having a varus knee, but it shouldn't present a problem to an experienced surgeon.
It usually happens when the cartilage in the lateral (outer) compartment of the knee has failed. That leads to a smaller gap on that side of your knee than there is on the medial side.
It's possible that your surgeon may recommend just replacing the lateral compartment of your knee, in a partial , or unilateral knee replacement (PKR).
If you decide to go for that, do make sure that your surgeon has a great deal of experience in doing partials, as they demand a certain skill set.
Also, insist that, if your surgeon sees any signs of osteoarthritis in another compartment of your knee, he/she will be prepared to do a Total Knee Replacement (TKR). Unfortunately, a lot of PKRs fail earlier than they should, because arthritis has spread to the other knee compartments.
In spite of the advertising in favour of a PKR, there is actually very little difference in recovery between the two types of knee replacement. In almost every case, having a PKR will not give you a faster or easier recovery than having a TKR.