Are you sure it's ACA? That's American Canine Association.....another recently popped up paper registry, similar to Continental Kennel Club and APRI. I don't believe ACA has conformation events...if they DO I would be very doubtful as to the quality of the entries...sorry
Maybe it's AKC?? Double check.
No, AKC nor CKC (Canadian Kennel Club) NOR UKC allows s/n dogs in conformation; however, CKC does have alter classes at specialty shows...however these classes are nonregular classes and do not count towards championship...i.e. no points are awarded. Now you can show in Veterans sweepstakes if your dog is s/n....and in regular veterans classes at independent specialties only..but NONE of this will apply to your dog.
To achieve Canadian championship a dog must accrue ten points, under three different judges with at least a 2 point win included in those ten points. My bitch just recently finished her Canadian championship in two weekends with two three point "majors" (a major is 3, 4 or 5 points--same in AKC) and four additional points. You don't ever have to win BIS. To achieve AKC championship your dog must earn 15 points with two major wins (3, 4, or 5 points) under at least 3 different judges. I have finished several AKC champions as well.
If your Dachshund is ACA registered and not AKC registered, honestly I would forget about it and just have him neutered...sounds like it is more others' idea than yours re: showing anyway!
Just neuter and enjoy him. If he is AKC and you are truly interested then talk to the breeder, research the standard, etc.....
I hope this helps and feel free to ask me any questions!