Some people thrash their pre-2013 motors for years on track and have no problems, but others get 6-10 days on track before they let go. Anecdotally it seems that if it doesn't go bang in the first 10 trackdays, you're probably fine for good.

However, replacement motors are 1. hard to find, and 2. expensive. So, better safe than sorry!

I'm replacing inlet and exhaust springs and retainers. They come as a kit (per valve) with the retainers etc all included with the new springs. They need to be the "2014 Spec" valve kits, part numbers 2R000037 and 2R000038. In terms of cost, they are 'sit-down-before-I-tell-you-so-you-don't-pass-out' prices.... roughly $900 per motor, just for the spring kits. Plus all the special tools needed, so you'd need an Aprilia mechanic. I bought all the tools a while back, and it was over $1k (and I got good pricing from Aprilia).

I have no idea how long it'll take to do (I haven't done it yet), but it's gonna be a fairly big job I suspect. The heads shouldn't need to come off.

Call Ben Reid. Get him to do it for you. He'll have the bits. And I suspect nobody would be quicker than Ben to do the work.