Check what you are allowed to do.....
There's a definitive list of items the pilot/owner is allowed to do which can be downloaded and used as your "bible" - but this is really stuff you can do during the year and at 50 hour check (you could always do most of this under the old system). But when it comes to annual, that must be done by licensed engineer (or his underlings). Some enlightened engineers might allow you to assist, but would expect you to do so under their supervision. There really isn't any way you can escape the cost of the annual inspection, so you need to choose an engineer that doesn't overcharge, yet does the job thoroughly. Only they can apply for the ARC, and again, you need to check charges for this.
The engineer needs to have the authority to apply himself, or if they have to go to another organisation for sign off, no doubt it will cost you more. The signatory has to pay an annual fee to CAA to be able to sign off ARCS. A fair-minded engineer will split that cost between the number of aircraft he looks after, so individual costs aren't too high.
NOTE: If you are applying the MIP and therefore using 100 hours between checks, you'll still need to change oil more often as recommended by engine manufacturer, and whilst you are at it, why not do the rest of a 50 hour check as you used to? Under MIP there's no obligation, but it's very sensible, and your engineer will appreciate that you have done and recorded it. I wouldn't want to keep flying for up to year without having the cowlings off at regular intervals and checking everything! The SDMP hardly saves you anything over the old LAMP system, but it does allow leeway on some time/age-related items, which might be significant.
You need to build a good relationship with your engineer! Good luck......