Sorry no guide experience in Huaraz (wah-RAHSS) but to bump the thread I'll give my experience birding the south/Carpa sector of Huascarán NP. Laguna Patococha was great for Puna Ibis, Puna Teal, Andean Goose/Gull/Duck, Giant Coot, many nesting Silvery Grebes. Songbird situation was light the day I went (rainy) but I got half a dozen high-altitude specialty passerines/flycatcher. Variable Hawk too but those are all over. I was there for work and my coworkers and I visited Pastoruri Glacier, so this was not a birding-specific run but if you're in that area that's where I'd stop.
Pastoruri itself is one of the disappearing tropical glaciers in Peru and a worthwhile experience. Drink coca tea while in the Andes to help with soroche (altitude sickness); I like the one with muña which is an Andean mint variety. End of the Climate Change Route to Pastoruri is at 5,000masl/16,400fasl. The 50ft tall Queen of the Andes (puya raimondi or puya gigante) and vicuña were the other highlights of that area.
A more actionable suggestion is if you speak Spanish at all to try asking on the Facebook groups for the Club de Observadores de Aves del Perú (could also use a machine translator like deepL which I think works better than google). There are chapters of COAP for Áncash and Cusco which might be able to help you, and the Lima chapter while not relevant to the areas is also full of helpful people who have birded all over the country.
If you find a guide not on this thread then I'd love if you posted another thread about it. I work in that area sometimes and would love a connection.
Buena suerte and hope you love Peru! 🇵🇪