I’d investigate the airframe and engine support separately.
For the airframe, UTVA’s official contact page is a starting point for asking about Aero 3 documentation, parts and possible specialist contacts. Current support and stock availability need confirmation; the manufacturer’s name alone doesn’t establish either.
For the engine, use its exact model and serial number when speaking to a supplier or overhaul shop. Lycoming’s distributor directory provides enquiry contacts, but confirm whether a supplier can actually support the installed engine and the parts you need.
Before committing, I’d want a named workshop willing and able to maintain the aircraft under its registration arrangements. Ask what manuals it needs, which jobs it can undertake and which components might require outside specialists.
The seller of the Aero 3 listed on CollectAirs states that a partially overhauled spare engine and additional parts are included. Request an inventory, identification details and condition records. Their practical value depends on compatibility, serviceability and what work remains.
Also establish the aircraft’s exact airworthiness status and any work or approvals needed for the intended operation.
If you have a recent supplier or workshop experience, please include the part or work involved and when it was supplied.