I would base the decision on the ride height of the front chassis. If the wheels are still about the same height below the upper fender as when new, meaning the springs are still strong, I would just replace the shocks. If the front fender is sagging, like noticeably lower than the rear fender, then I would replace the strut assembly - most likely with the Toyota OEM part since it is not substantially affected by towing as compared with the rear. Many OEM parts are available from Amazon. Just get the part number from the dealer part department with your VIN.
In answer to your question, Yes, you can replace just the shock absorber in the front.